Fourth wall

The fourth wall is the imaginary "wall" at the front of the stage in a traditional three-walled box set in a proscenium theater, through which the audience sees the action in the world of the play. When speaking directly to the audience through the camera in a film or television program, it is called "breaking the fourth wall." The technique of breaking the fourth wall can be seen in various television programs, especially situation comedies, in animated cartoons, and in films.

Opening Credits

 * The theme song ends with Candace pointing out that "Phineas and Ferb are making a title sequence."
 * In the same manner, Candace points out that "Mom, Phineas and Ferb are making a Christmas special" at the end of the title sequence unique to "Phineas and Ferb Christmas Vacation!".
 * Also in the same manner, Candace yells out that "Mom, Phineas and Ferb are making a Halloween special" after the title sequence for "That's the Spirit".
 * In an ad where Phineas narrates about the dangers of the internet universe, in the same manner, Candace points out that "Mom, Phineas and Ferb are making a public service announcement".
 * On the Phineas and Ferb Disney Channel old website, upon going there, Candace can be heard saying, "Mom, Phineas and Ferb are building a web site!"
 * At the end of the Take Two with Phineas and Ferb theme song, Candace says "Mom, Phineas and Ferb are making a talk show!"
 * On the "Across The 2nd Dimension" DVD, one of the Easter eggs has Candace pointing out, "Mom, Phineas and Ferb are making a DVD!"
 * On an ad for Disney's Phineas and Ferb: The Best LIVE Tour Ever!, Candace shouts "Mom, Phineas and Ferb are making a live stage show!"

Season 1

 * When Mom thinks the boys riding the horses is cute, Phineas looks at the audience and says "She means well" ("The Magnificent Few").
 * Dr. Doofenshmirtz clears his throat to prompt the running of a dramatic musical string that has failed to run on cue. ("One Good Scare Ought to Do It!").
 * Phineas is wondering where the backgrounds in the song History of Rock are coming from. ("Dude, We're Getting the Band Back Together").
 * Ferb mentions that their projects would usually be finished after a montage. ("Voyage to the Bottom of Buford")
 * Perry looks directly at the camera after noticing that the elevator is broken. ("Got Game?")
 * In the beginning, Phineas and Ferb are in front of a curtain warning the audience that they may be emotionally scarred by the coming episode. Later, Candace asks Reginald to tell his story of their ancestors in color. Phineas isn't pleased of the resolution Candace favors the story in and suggests muted color. ("The Monster of Phineas-n-Ferbenstein")
 * While dancing under the effect of the Dance-Inator, Dr. Doofenshmirtz speaks to the audience telling them that the platypus is leading. ("Out of Toon")
 * When Perry is invited in by Dr. Doofenshmirtz, Agent P waggles his eyebrows while looking at the audience, in a manner similar to that of Groucho Marx. ("Flop Starz")

Season 2

 * When Dr. Doofenshmirtz shows Perry the invention, he says "Behold... beholding, beholding, beholding, and scene!" ("The Chronicles of Meap").
 * Dr. Doofenshmirtz asks where the lightning is coming from ("Oh, There You Are, Perry").
 * Isabella and Gretchen wipe the camera during Phintastic Ferbulous Car Wash ("At the Car Wash").
 * Phineas references the use of storm clouds to show negative impact before looking at the camera ("Phineas and Ferb Christmas Vacation!").
 * Candace tells someone in the show's audience to hang up ("Candace's Big Day").
 * When Dr. Doofenshmirtz is showing his De-Evolutionator, he says "Can you all see in the back row," to the audience ("Phineas and Ferb Hawaiian Vacation").
 * An advertisement appears saying "You're watching Television!". Phineas says that it is interrupting a visual gag ("Phineas and Ferb Summer Belongs to You!").
 * Phineas says "No matter where we go, Ferb knows every one". He is talking to the audience. ("Phineas and Ferb Summer Belongs to You!")
 * At the end, Phineas says have fun everybody to the audience. ("Wizard of Odd")
 * One of the floors in Phineas and Ferb's building is called the "studio audience floor" ("The Doof Side of the Moon").
 * Carl replied Monogram that Phineas & Ferb is a cartoon and Major Monogram had told him about breaking the fourth wall ("Make Play").
 * Buford calls the boys with the flyers "extras." Also, Doofenshmirtz acknowledges the cut to black at the end of the first act. Major Monogram also breaks the fourth wall by saying "Come on!" when the end logos pop up ("Rollercoaster: The Musical!")
 * Major Monogram breaks the fourth wall by calling Cindy an animated member of the studio audience. ("Phineas and Ferb Musical Cliptastic Countdown")
 * Dr. Doofenshmirtz complains about the festival being so loud that he can't hear his own evil jingle ("Attack of the 50 Foot Sister")
 * Perry looks at the camera angrily after a briefing from Monogram which he said to be careful about the paper ("Backyard Aquarium").

Season 3

 * Baljeet talks with Buford about the opening titles. Later on, he questions how everyone is running in slow motion. ("Canderemy")
 * Candace mentions that Phineas has a catchphrase to say. ("Run, Candace, Run")
 * Baljeet argues with the male singer from Lunar Taste Sensation. ("Moon Farm")
 * After Doofenshmirtz exclaims to Perry that they're not in a sitcom, they stare directly at the camera nervously supposedly realizing that his statement is false. ("A Real Boy")
 * Phineas says "We'll be right back" before a commercial break, and fixes the time of day his flashback is being shown. He also comments on the time of day in the flashback. ("My Fair Goalie")
 * Ferb looks at the camera while saying "Our dad sells antiques". ("Ferb Latin")
 * Ferb states that Perry is having a "ripple dissolve" and he must be having a flashback. Phineas then comments on how he can't see the flashback. ("Doof Dynasty")

Phineas and Ferb The Movie: Across the 2nd Dimension

 * In the song Everything's Better with Perry, Phineas and Ferb broke the fourth wall by staring at the camera.
 * In the song Brand New Best Friend, Dr. Doofenshmirtz and his second dimension counterpart mention Lorenzo Lamas playing Meap in "The Chronicles of Meap".
 * In Summer (Where Do We Begin?), Phineas' eyes stare directly at the screen.
 * At the beginning of the cut song Mysterious Force, Candace sings directly to the audience.