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 theatre, 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 "Phineas and Ferb are making a Christmas special" at the end of the title sequence unique to Phineas and Ferb's Christmas Vacation.
 * In an ad where Phineas narrates about the dangers of the internet universe, in the same manner, Candace points out that "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!"
 * In Take Two with Phineas and Ferb starting, Candace says "Mom, Phineas and Ferb are making a talk show!"

Season 1

 * When Perry is invited in by Dr. Doofenshmirtz, Agent P waggles his eyebrows while looking at the audience, in the same manner as Groucho Marx ("Flop Starz").
 * 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 ahem when the dramatic music does not come on at one point ("One Good Scare Ought to Do It!").
 * Phineas asks where the backgrounds are coming from during Danny's Story ("Dude, We're Getting the Band Back Together").
 * Ferb says that building their Big Idea takes about a montage ("Voyage to the Bottom of Buford").
 * Perry looks directly at the camera when the elevator is broken ("Got Game?").
 * In the beginning, Phineas and Ferb are in front of a curtain and tells the audience that what they are about to see can scare, or even horrify, them. Also, Candace asks Reginald to tell the story in color ("The Monster of Phineas-n-Ferbenstein").
 * While dancing after hit by the Danceinator Dr. Doofenshmirtz speaks to the audience telling the platypus is leading ("Out of Toon").

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!").
 * 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 rooms in Phineas and Ferb's building is called the "studio audience room" ("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's Musical Cliptastic Countdown")

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 supposingly realizing that his statement is false. ("A Real Boy")

Phineas and Ferb The Movie: Across the Second Dimension

 * In the song A Brand New Best Friend (and It's Me), Dr. Doofenshmirtz and his second dimension counterpart mention Lorenzo Lamas playing Meap in The Chronicles of Meap.