Doofenshmirtz comments in "A Real Boy" on how Vanessa overhearing something he said out of context was like something on a sitcom, but he ends up mainly Breaking the Fourth Wall more than anything else.
Dr. Doofenshmirtz does this frequently, too... like in "It's About Time!" discussing how he wants to hurt Perry the Platypus "the right way, with cartoonish acts of violence and hare-brained schemes."
Another Dr. Doofenshmirtz example: when most of the main characters are in space for one episode, he exclaims "why is there so many people in space? What's up with that?"
In the episode where Phineas and Ferb go to the mall and Ferb tries to help Vanessa get the Pizzazium Infinionite her dad wants, but at the end, Perry tricks the security guards into thinking Doofenshmirtz was going to steal it unbenknownst to him. As they drag him away, he says "Wait you canít take me, I donít have anyone to curse!"
Another one lampshades the length of the series, with Phineas saying, "You're right Ferb. It DOES feel longer than 104 days."
Buford also says "Are you sure it's only been three months? Because I added up the stuff we've been building and we're way over 115..."
In "Fly on the Wall," Doof laments that the summer seems to be going on forever.
In one episode, Stacy says "Hey, whereís Perry?" and Candace gives her a dumb look. Stacy responds with "What? Iím like the only person who hasn't said it yet."
In Irving's debut episode, he asks if he can "Say the Perry thing." Also:
Phineas: Ferb, I know what we're going to do today.
There is a moment in "The Lizard Whisperer" where Phineas calls Steve the chameleon a dinosaur, but Isabella manages to question his terminology. Phineas replies that he uses dinosaur simply because it's "cooler".
Doofenshmirtz often gets angry at Perry the Platypus for breaking holes in his walls and doors. This is taken to a new level in "Tri-Stone Area," when Caveman Doofenshmirtz obviously complains about this without even speaking English. It's pretty obvious the writers are adding even more Running Gags as the series goes on.
When Phineas and Ferb made all the kids ninja suits to wear Buford asks Phineas which direction he's facing. Phineas says it's a good question before completely turning his eyes to the right before responding, "Left".
During one of Perry and Doofensmirtz's fights. Doofenshmirtz states "But this is real life" cue Perry and Doofenshmirtz awkwardly looking at the audience for a few seconds. Also is a case of Breaking the Fourth Wall
Canderemy makes fun of the Slow No trope. When the robotic dog gets shut down and drops the device that can return Candace and Jeremy to normal, the program goes into dramatic slow-mo and Phineas, Candace, Isabella and Buford all yell "Nooo" frantically (save for Ferb, who blinks in slow motion), complete with loud distorted voices. The only exception is Baljeet, who merely stands in his place and does the lampshade by asking why are they doing that.
It is sometimes acknowledged that Major Monogram's eyes are positioned on the same side of his nose, in reference to the way in which he is drawn.
Doofenshmirtz: Wait a minute, wait a minute. How did you get the sunglasses to go on one side of your face? Who made these, M.C. Escher?
In the opening song of "Save Summer", "Summer all over the World", the whole world is celebrating Summer via a concert, even people in the Southern Hemisphere. The song realises this and says that it's a different time of year in the south.