Isabella and Phineas's relationship

Isabella Garcia-Shapiro has a huge crush on her neighbor and best friend Phineas Flynn. She has romantic daydreams about him and hopes to marry him one day. She never tells him, though. Phineas's feelings for Isabella on the other hand are relatively unknown, varying from platonic to romantic.

Isabella's Opinion of Phineas
Isabella has a huge crush on Phineas. It is currently unknown how, why, or when she fell in love with Phineas. She uses her position as Fireside Girls troop leader to stay near him and assist with his Big Ideas, under the guise of earning the "Help Thy Neighbor" patch among other more specific patches. Although she usually just speaks to him as a friend, she occasionally attempts to flirt with him and cutely greets him with the phrase "Whatcha doin'?" almost every time they first see each other each day ("Isabella and the Temple of Sap", "The Fast and the Phineas", "The Beak", "Phineas and Ferb Summer Belongs to You!", "Canderemy").

Sometimes she gets carried away with her feelings and daydreams, resulting in not hearing a thing Phineas asked her to ("Isabella and the Temple of Sap", "Bee Day"), and accidental confessions of her affection, although Phineas does not seem to notice. She has even directly referred to Phineas as "The very thing I live for." One of her fantasies involves Phineas becoming a flying centaur and them riding off together. She is a little annoyed that Phineas focuses so much on his projects instead of noticing how she feels about him. She is also known for fantasizing about their marriage ("Comet Kermillian", "Phineas and Ferb Summer Belongs to You!", "Rollercoaster: The Musical!", "Candace's Big Day", "Phineas' Birthday Clip-O-Rama!", "Isabella and the Temple of Sap").

Isabella also jumps to Phineas's defense when he is in danger or insulted. She doesn't seem to care when Phineas uses her catch phrase, though she gets upset whenever someone else does. She is sometimes saddened because Phineas doesn't notice her and doubts his feelings for her ("The Beak, Phineas and Ferb Summer Belongs to You!", "Raging Bully", "One Good Scare Ought to Do It!", "Gaming the System", "Thaddeus and Thor", "I Scream, You Scream", "At the Car Wash", "That Sinking Feeling", "Phineas and Ferb Christmas Vacation!", "Out of Toon", "Suddenly Suzy").

Phineas's Opinion of Isabella
Phineas' feelings for Isabella are somewhat unclear. Phineas usually seems oblivious to Isabella's feelings. At the very least, she is one of his best friends. However, he often shows signs that he likes her as more than a friend, much like she does for him. He sees love from a formulaic point of view, trying to recreate it like one of his projects and not truly understanding what it means. Whenever she hints at her crush to him, he either misinterprets the comment as platonic or gets confused, either way he never gets what Isabella wants: to spend quality time alone with him. One example is when Isabella invites him to the "Night of the Falling Stars Girl's Choice Dance" as her date, Phineas brings Ferb to the event as well, possibly assuming she meant all three of them would go together as friends ("That Sinking Feeling", "Out to Launch", "The Fast and the Phineas", "Run Away Runway", "Comet Kermillian", "Candace's Big Day", "Canderemy"). It's possible the reason why Phineas doesn't pay attention to Isabella's interest in him is because he is too busy with his Big Ideas.

Phineas can be seen to believe that Isabella is very cute, to the point of having to recalibrate his "Cute Tracker" to keep it from confusing Isabella for Meap. Phineas has also shown concern for Isabella's safety and rescued her on occasion. He seems to have trouble lying to Isabella; when trying to lie, he rubs or scratches his ear and speaks nervously, yet he casually lies with ease to both Linda and Candace (Although he may not even know he is lying, since these lies are usually caused by the ambiguity of the question). He is shown to not be nervous whenever Isabella asks him to go anywhere with her, and does not seem to be surprised when she hugs or taps him, like when she hugs him from behind or when she momentarily tries to rest her hand on his shoulder. Phineas sometimes appears to be bored while going over the Big Ideas, but when he talks with Isabella, he seems happier ("One Good Scare Ought to Do It!", "Canderemy"). On his birthday Phineas states that he enjoys being around the people he loves while he says this a tear runs down Isabella's face. This may mean that Phineas may like her now as more than a friend ("Phineas' Birthday Clip-O-Rama!"). However considering the ambiguity of his usage of "love" it may only mean that he enjoys being with his closest friends ("The Chronicles of Meap", "Gaming the System", "Hide and Seek", "The Beak", "Oh, There You Are, Perry", "Phineas and Ferb Summer Belongs to You!", "Last Train to Bustville", "Canderemy"). There are many small points where Phineas shows (or it seems so) affection towards Isabella. For example, while the gang is running through the grand entrance for their Aunt Tiana's wedding, Phineas exclaims, "Looking good Isabella!", however, this may have been just a coincidence as they were running through the grand entrance sequence and Phineas was double checking how things were going. Of coarse, Phineas had not said anything of the sort to anyone else who was running through the sequence. ("Candace's Big Day") Phineas also worries Isabella will get hurt when giant Buford comes up to her, and when she is stampeded by giant chinchillas ("Gaming the System", "Der Kinderlumper", "Terrifying Tri-State Trilogy of Terror"). Unlike his other friends, Phineas is willing to put the day's project on hold if Isabella can't take part in it. ("I Scream, You Scream", "Bee Day", "Just Desserts")

Phineas may have romantic feelings for Isabella because after Isabella kisses him, he seems surprised but delighted. He then tries to stop Carl from shooting the Amnesia-Inator, by yelling "Wait! Wait! Wait!", possibly because he doesn't want to forget the kiss, wanted to return the feelings, or wanted to tell Isabella something, but he is unsuccessful (Phineas and Ferb The Movie: Across the 2nd Dimension).

Phineas's Big Ideas for Isabella
Many of Phineas's Big Ideas are actually wild projects for Isabella, and sometimes to a greater extent the Fireside Girls, however this may not mean anything considering that he has also made projects for Baljeet, Buford, Candace, his Mom and to some extent Irving. For instance:


 * Phineas made a giant ice cream sundae for her after she had her tonsils removed ("I Scream, You Scream").
 * When Isabella's dog Pinky swallowed her sash, he and Ferb built a shrinking submarine to retrieve it ("Journey to the Center of Candace").
 * Isabella was telling Buford how Table Soccer could be the biggest game in the world and girls could still beat boys when she realizes that was what to do for the day. Phineas almost immediately replied that he was on it ("Got Game?").
 * On the day Isabella got hiccups, Phineas convinced Ferb and his friends to build a haunted house to scare them out of her, and he dedicated the whole day to her. He also held her hand all the time going through the haunted house alone. ("One Good Scare Ought to Do It!").
 * Phineas built a "Rainbow-inator" for Isabella when he thought she expressed a desire to see a rainbow, having never seen one before. When she clarified that she wanted to see a unicorn, Phineas decided that he and Ferb would find her one the next day ("Hail Doofania!").
 * Phineas held a game show so Isabella and the Fireside girls could get their broadcasting patches ("Let's Take a Quiz").
 * Phineas and Ferb assisted Isabella and the Fireside Girls in building the world's most elaborate automated car wash when they needed to save the Star-nose mole through means of fund-raising ("At the Car Wash").
 * Phineas made everyone stop when they were riding their bikes so they could pump up Isabella's flat tire on her bike ("Just Passing Through").
 * Phineas asked Isabella what patch she and the Fireside Girls haven't earned yet. She tells him it was a Rodeo Clown Patch. Therefore, he and Ferb held a robot rodeo for them to earn it ("Robot Rodeo").
 * Phineas saw Isabella was sad when she and the Fireside Girls weren't able to get their Desert Tracking Patch due to the rain, he and Ferb quickly made a bio-sphere to help them along with earning other patches ("The Great Indoors").
 * Phineas creates a super grow lamp for Isabella's Bamboo plant so it could get some more sunlight ("The Curse of Candace").
 * Phineas helps her by cloning some potatoes using Buford's last potato chip so that Isabella's Nana can make latkes for the Latke Festival at the Danville Senior Lodge ("Lotsa Latkes").
 * Phineas was originally going to help Isabella get her surfing patch, but they change their minds in order to help squirrels ("What'd I Miss?").
 * Phineas let Isabella borrow the sorbet maker that will turn her and the Fireside Girls into bees to earn their Bee Keeping Patch ("Bee Day", "Bee Story").
 * When Isabella tells Phineas that Pinky has gone missing, Phineas and Ferb build the dog systematic helmet to find him ("Where's Pinky?").
 * Phineas and his brother organize a birthday party for Isabella. ("Happy Birthday, Isabella")

Romantic Moments

 * Phineas looks at Isabella flirtatiously when she asks him if she and the Fireside Girls can be lifeguards ("Lawn Gnome Beach Party of Terror").
 * After Isabella gives Phineas some juice during the pit stop and mentions that his helmet is "so manly", Phineas gives her a pleased reaction ("The Fast and the Phineas").
 * Phineas looks at Isabella flirtatiously as she says "Wow, Phineas! Another strike!" ("Bowl-R-Ama Drama").
 * Phineas and Isabella look at each other endearingly as Isabella tells him there's an M in Time Machine ("It's About Time!").
 * Phineas held Isabella's hand as they went through Phineas and Ferb's haunted house designed to scare away her worst case of hiccups ever ("One Good Scare Ought to Do It!").
 * Phineas has had to recalibrate his "Cute Tracker" so as to cancel out Isabella's perceived "cuteness" ("The Chronicles of Meap", "Meapless in Seattle").
 * Phineas and Isabella flirt with each other by repeatedly saying "coincidentally" before each sentence ("De Plane! De Plane!").
 * After singing Come Home Perry, Phineas and the others rush up to hug their pet platypus, but instead of hugging Perry, Isabella ended up hugging only Phineas ("Oh, There You Are, Perry").
 * When Isabella was put in danger by a mechanical bug (when they were all small), Phineas quickly rescues her by swinging by on a thread and carrying her with him to safety. Also for a brief second, Phineas took Isabella's hand and helped her into a paper airplane ("Hide and Seek").
 * Phineas invited Isabella on the romantic cruise. While on the boat, he tells her what else he has in mind, causing her to blush once, then takes her hand leading her into the romantic dinner room, but Isabella is annoyed when learning it's for Baljeet and Mishti instead, and isn't theirs. Later, they shared a "fun preserver" after the ship sank. Also, at the end of their ride on the "fun preserver" Phineas says that 'this romance thing' is fun, and that they should do it more often, to which Isabella replies, using a play on a common catchphrase from the show "yes, yes we should." ("That Sinking Feeling").
 * When Phineas worries about him being the reason for Santa Claus not coming to Danville, Isabella does her best to cheer him up. In the song Danville for Niceness, Phineas looks at Isabella endearingly as she sings a duet with him ("Phineas and Ferb Christmas Vacation!").
 * Before recognizing their friend Steve, Phineas and Isabella were frightened and ran away together. When searching for Steve, Phineas and Isabella called his name at the same time ("The Lizard Whisperer").
 * Isabella wanders into their yard and sings Whatcha Doin'?, in which she states that he has no idea that everyday she comes over just to see him. As Isabella says "Wow, chatty!", Phineas looks at her slightly flirtatiously. He also looks at her that way in the song Rollercoaster, however, he did look that way throughout most of the song. Also, throughout the lines "We go: Ah, ah, ah!", he seems to be leaning towards her and pulling her closer to him slightly on the "Ah, ah, ah!" ("Rollercoaster: The Musical!").
 * Isabella decides that today is the day she will finally spend some time alone with Phineas. She asks him if he'd like to see the new Stumbleberry Finkbat movie, saying she can't invite Ferb because she "only has one extra ticket, and the movie has already sold out." Phineas says he will as soon as they are down with the day's project. However, problems arise and Isabella is repeatedly forced to wait. When it is finally time to go to the movie, a stray beam from Doofenshmirtz's new invention, which causes two beings to fuse together, hits Phineas and Ferb, resulting in the two becoming one being. As a result, all three can now go to the movie, much to Isabella's disappointment, as Phineas and Ferb now count as one being ("Canderemy").
 * While on the hot air balloons, Isabella's balloon is behind Phineas's. Isabella asks him what he's doing, seeing him fidgeting with something on his balloon. He explains that his wheel is broken, but stops mid-sentence because he hears something behind him. He turns around to see Isabella, who asks if he needs help fixing it. Phineas replies by asking her to hold the wheel still. Isabella immediately jumps on the opportunity and holds the wheel still, obviously overjoyed that she can put her arms around Phineas. Phineas doesn't seem to mind, and replies by saying she's holding it perfectly, possibly hinting that he likes having her arms around him. Isabella smiles and replies with a common catchphrase from the show, "Yes, yes it is." Phineas and Isabella then stay in the same balloon together for the rest of the ride ("Last Train to Bustville").
 * Phineas explains that the teleport function of his and Ferb's prototype cellphone, built for Candace, will "take you to the place or person you're trying to reach." He demonstrates this by asking Isabella to stand in the driveway, to which she willingly agrees. Phineas specifies Isabella's name to the phone, and is transported directly beside her - so close, in fact, that their noses touch. Isabella asks Phineas what he's doing, to which Phineas responds "I'm transporting!" They don't move, pull their noses away, or appear flustered throughout the exchange. Isabella seems very pleased with the close contact - that is, until Phineas transports back to the garage and she angrily responds with a "Dang it!" ("Candace Disconnected")
 * As the song Aerial Area Rug starts, Phineas reaches out for Isabella's hand to help her onto the flying carpet. They are also seen looking into each other's eyes, lying down close to each other, or just sitting down together away from everyone else throughout the duration of the song ("Magic Carpet Ride").
 * After thwarting 2nd Dimension Doofenshmirt'z plan, Carl was going to wipe the memories of everyone who found out that Perry was a secret agent using a machine called the "Amnesia-nator". Isabella asks Major Monogram if the machine would make them forget everything that happened that day, he assures her of it, and she replies with "Good!" then grabs Phineas and kisses him. Phineas gasps, smiles at Isabella and says her name, sounding pleasantly surprised. She then tells Carl to "hit it", much to the dissatisfaction of Phineas, who proceeds to cry out, "Wait, wait, wait". This indicates that he wanted to remember this moment or to return his feelings for her, even if it were just for a moment, but he is unsuccessful (Phineas and Ferb The Movie: Across the 2nd Dimension).
 * While Phineas is explaining the Tour de Ferb course to everyone, Phineas compliments Isabella by remarking, "Isabella was kind enough to enlist the help of the Fireside Girls to make the course." As Phineas says this, Isabella blushes and smiles ("Tour de Ferb").
 * Isabella gets "Share A Turn" and she uses some balloons to fly over to where Phineas was ("Skiddley Whiffers").
 * Phineas compliments Isabella on her "nice fairy princess costume", though when Phineas asks her where she got it, she initially replies that she's not wearing a costume. When Phineas replies with a mere "Okay" she admits that she got it at the Googolplex Mall in a disappointed tone. ("That's the Spirit")
 * Isabella and Phineas look at each other flirtatiously when Isabella hopes Phineas will get a bulls-eye ("Bullseye!").
 * Isabella looks at Phineas flirtatiously when he is explaining how Ferb Latin works. Also, Phineas and Isabella sing and dance together during most of Ferb Latin ("Ferb Latin").
 * As Isabella walks towards the stool to sing Let it Snow, Let it Snow, Let it Snow Phineas looks at her endearingly. The song Let it Snow, Let it Snow, Let it Snow has a romantic nature and during the song Isabella lightly kisses a snowman shaped like Phineas on the nose. The snowman quickly melts after she does this. She also forms a heart with her fingers around a Phineas shaped silhouette in a window. ("A Phineas and Ferb Family Christmas").
 * When Phineas first sees Princess Isabella, he dreamily admires her. Then, when Phineas and Ferb come to rescue her from Doofus Khan, she thanks and hugs Phineas. After the escape, Doofus Khan finds them again and Isabella hides behind Phineas; they escape together after Doofus Khan's dragon fell on top of the giant terracotta warrior after the battle. However, these events partially don't count due to the fact that this episode is in a parallel world. ("Doof Dynasty")
 * In the song S'Fall, Phineas and Isabella jump into the pile of leaves holding hands. Later on, they can briefly be seen dancing together. ("Minor Monogram")
 * Phineas and Isabella share a jet ski when following Candace and Crikey through Danville sewers and canals. They are constantly smiling at each other during the ride and he is holding her shoulders and later hips for support. When they are somehow separated during the ride, both are disappointed when they find that they are not riding with each other anymore. ("What A Croc!")
 * Isabella turns a "Romantic dinner for two" into a smoothie for Phineas. Phineas turns it down and Isabella believes he is rejecting her again. However, when Phineas tells her the reason is that he does not like zucchini, Isabella gets a surprised look on her face. ("Doofapus")
 * Isabella reaches for Phineas's hand, but grabs Ferb's by mistake. ("When Worlds Collide")
 * Isabella hints to Phineas about the traditional New Year's kiss at midnight, but Phineas doesn't get the hint and suggests building their own version of the New Year's Eve ball drop instead, which leaves Isabella disappointed. Later, during the song, they were seen dancing together in two scenes. At one point, Phineas performs the dance from "Gangnam Style", and Isabella also does the dance with the Fireside Girls in the very next shot ("Happy New Year!").
 * They both sit together when riding the tooth buggy of the Dental Hygienoshpere ("Bully Bust").
 * Phineas tells Isabella he'd do anything for a friend only Isabella misinterprets this and daydreams about him ("Bee Day").
 * Phineas offers Isabella some ice tea, saying "You want some honey?" She is startled by that comment, but he then repeated himself revealing he was offering her some honey for her tea ("Bee Story").
 * After the giant ball of water is finished, Phineas grabs Isabella's hand and leads her off to surf with him. They are also seen surfing and are on their surfboards for nearly the entire time  ("Great Balls Of Water").
 * They lock eyes with each other periodically on the climbing wall ("Just Desserts").
 * Phineas and Ferb give Isabella a big birthday party, but all she really wants is to be alone with Phineas. At the end of the party, she expresses adoration for his (-inator-assisted) grand finale: butterflies. After the party, Phineas asks if she wants to go out with him and Ferb for ice cream, but Ferb discreetly opts out, allowing Phineas and Isabella to go out together ("Happy Birthday, Isabella").
 * While surfing asteroids, Phineas and Isabella hold hands. Isabella says that the way the big spaceship is shaped like Phineas' head is dreamy and that she gets distracted when Phineas is in a spacesuit ("Phineas and Ferb: Mission Marvel").
 * When Phineas decides to be Paris in their Trojan War reenactment, immediately Isabella says she'll portray Helen of Troy. While riding in the chariot, Isabella has her arms wrapped around Phineas ("Troy Story").
 * When Isabella dresses as Cinderella, she "accidentally" drops her shoes for Phineas to pick it up but he fails to notice. Towards the end of the episode, Phineas asks a sad Isabella what was wrong, and she states that she ran out of shoes and is now barefoot. Phineas responds by taking off his shoes and dancing with her, saying it's better to dance with your shoes off anyway. ("Druselsteinoween")
 * When the gang is done with the chores and Phineas asks everone what they want to do with their extra time, Isabella proposes that they should start formerly courting (be involved romantically) as she looks at him dreamily ("Steampunx")

During the Search for Meap and their Trip to Seattle
One of the moments Phineas clearly showed more-than-platonic feelings for Isabella occurred when the alien Meap arrived and when he later returns.

When Meap crash-landed in the Flynn-Fletcher backyard, Phineas proclaimed him to be " the most adorable thing in the world" and immediately decided that he and Ferb would help fix his spaceship. However, they lost track of Meap when he followed Candace to the Bango-Ru convention (with Meap thinking that Candace was also a security agent). In order to find him, Phineas created a "Cute Tracker" that used to be Ferb's old GPS device. Seeing this as an opportunity, Isabella tried to convince Phineas that she's cute too. Unfortunately, it constantly received a "cute interference" and Phineas inadvertently upsets her for saying that she wasn't the cause of the cute interference. Isabella immediately saw this as Phineas thinking that she wasn't cute, and got upset every time Phineas said that she wasn't causing the cute interference.

Isabella finally told Phineas that she thought she might be the cause of the cute interference when he was having a hard time picking up Meap's cute signal inside Mitch's ship, but he then assured her that that was completely impossible and he explained that he knew her cuteness would disrupt Meap's signal and he programmed the tracker to ignore her. To prove it to her, he reversed the system that prevented the Cute Tracker from recognizing Isabella. The machine then overloaded due to an excessively strong cute signal, showing that Phineas thinks Isabella is immeasurably cute. ("The Chronicles of Meap")

When Meap returns to save Phineas and Ferb from Mitch, Phineas carries Isabella by the waist to safety while trying to evade threatening laser beams. Later, when Phineas becomes hypnotized by Mitch's cuteness, Isabella is the only one able to snap him out of the trance. Phineas alludes to Isabella's own cuteness as a 'scientific fact', claiming that it 'goes right to her core'. He also says he learned "a valuable lesson" while looking at Isabella, though did not elaborate on what it was. ("Meapless in Seattle")

During Phineas and Ferb's career as "The Beak"


The only moment (so far) where Isabella truly felt neglected by Phineas and actually doubted her feelings for him is when Phineas and Ferb unexpectedly became the new town superheroes, masquerading as "The Beak."

Isabella wants to interview Phineas and Ferb to get a patch; however, she misses them and has to do an alternate story on The Beak, who she is unaware is actually Phineas and Ferb. She calls Phineas and was annoyed at him for missing the interview. He decides to tell her about he and Ferb being "The Beak", but is unable to at the time because of Khaka Peü Peü's interruption. When "The Beak" is laying powered down after being slammed into a building during this time, Phineas hears Isabella say, "Where's Phineas? He'd know what to do!" The Beak then powers up and continues to fight. Khaka Peü Peü then tells Phineas that he will get him through what's most important to him. This causes Phineas to remark that they can't tell Isabella that they are the Beak now because it would put her in danger, implying that he considers Isabella important to him. It could be believed that Phineas really cares about Isabella. Isabella swoons for "The Beak" many times during The Beak's Theme Song, not realizing that it was still Phineas she was swooning for.

Isabella is upset and confused as to why Phineas keeps rejecting her and disappearing when she needs him. When Isabella climbs atop City Hall to take pictures, "The Beak" slams into the building, knocking her over the edge. Khaka Peü Peü then knocks a Bango-Ru billboard off an adjacent building, leaving Phineas the dilemma of saving Isabella as she clings to the side of the building, slowly losing her grip, or saving the bystanders from the billboard. To solve this, Phineas jumps out of the suit and grabs her hand before she falls, leaving Ferb to dispatch the billboard. Later, Phineas then reveals that he was the Beak to her and apologizes for not telling her. She realizes that Phineas was just trying to protect her, and apologizes for doubting him. She flirts with Phineas in the end saying he's really brave, to which Phineas responds by noting she was brave too ("The Beak").

During their Trip Around the World
During their trip around the world, Isabella tries to get Phineas to get in the spirit of being in the City of Love, but he is focused on using the stop in Paris to repair the plane. She expresses her feelings in the song City of Love, a bit despondent that Phineas is oblivious to the romantic nature of the city. When Phineas points out to Ferb that he thought he and Vanessa would avail themselves of romantic nature of Paris, Isabella becomes extremely frustrated that he missed the point, snapping a pencil in the process. She then imagines her own head exploding when Phineas does the same with Candace about her and Jeremy, causing Phineas a small amount of distress and/or puzzlement.

On their way back to Danville, the baguette boat falls completely apart, and they crash land on a deserted island with only a "big fat ox" for company. Desperate for a way off the island, all the while gradually losing his optimism, Phineas digs a huge hole in the sand in search for something useful. Buford's taunts don't help him. Isabella goes off alone and cries. Ferb walks up to her and hands her a handkerchief. Then she pours out her heart to Ferb, sobbing that she and Phineas were together in Paris and he didn't even notice her. She feels like giving up, and complains he won't even do something as simple as enjoying the beautiful sunset with her. At this moment Phineas runs up to her and suggests that they could build a tunnel under the ocean. He doesn't attempt this and instead he gives up, sits to the ground and says they can at least enjoy the beautiful sunset. At first Isabella enjoys it, but then she sees that Phineas's spirit is broken, and something clicks in her head. She realizes that this wasn't the spectacular, confident boy she fell in love with and tells him angrily that he can't enjoy the sunset, because giving up wasn't part of his plan. Isabella reminds him of everything he did in his life, almost confessing about her crush on him. She then mentions Ferb's map, starting to say that giving up wasn't part of the plan he marked out on it. Inspired, he cuts her off and hugs her, leaving her in a sort of trance. He then leaves her to get to work on their way to get off the island. Back in Danville, with only a second to spare, they make it just in time to beat the sun, and the other Fireside Girls have a welcome home party ready for them. Isabella hugs Phineas from behind, saying, "You guys are amazing!" In response to this, Phineas holds her hands, looks back and smiles. A musical number breaks out, and Isabella and Phineas dance and sing a duet, Summer Belongs to You. Phineas often reaches over to hold her hand throughout the song and it seems he becomes even more comfortable touching her ("Phineas and Ferb Summer Belongs to You!").

Potential Marriage
When Phineas, Ferb, Isabella, and Candace time-traveled to the future, Candace's future daughter Amanda noted that Isabella looks like "Aunt Isabella". Thrilled, Isabella realized that she will marry into the Flynn-Fletcher family in 20 years and exclaimed to Candace that she must have married Phineas. However, Candace reminded her that she could have married Ferb, which sent Isabella into speechless shock ("Phineas and Ferb's Quantum Boogaloo"). It is also possible that she just remained good friends with the Flynn-Fletcher family, so that Candace's kids call her "Aunt Isabella" even though they are not actually related.

When Candace was planning her Aunt Tiana's wedding, Phineas said, "I got to have her plan my wedding. Ferb, make a note of it," to which Isabella interrupts with, "I got it," indicating that she intends to one day marry Phineas ("Candace's Big Day"). When Isabella helped create a digital video for Phineas's birthday, she created a digitally edited video for herself with Phineas saying, "We'll-be-together-forever-Isabella" and "Isabella-will-you-marry-me?" ("Phineas' Birthday Clip-O-Rama!"). Many of her dreams always end with Phineas asking her to marry him ("Isabella the Hero").

Background Information

 * The upcoming episode "Act Your Age" and its song will be about Phineas and Isabella's relationship.
 * Ferb is aware that Isabella wants to spend time with Phineas, as seen when Isabella spills her feelings on the island in "Phineas and Ferb Summer Belongs to You!". In "Happy Birthday, Isabella", this is part of the reason Ferb lets Isabella and Phineas have alone time.
 * A future episode shows Isabella wanting to have a relationship with Phineas.