These come up from time to time. Sometimes played straight (the time Candace got her head stuck in the sink), and, since one of the creators of the show used to work on Family Guy, there will obviously be some subversions (Dr. Coconut).
- Whatever Linda did to embarrass Candace at her 5th grade graduation "with the inflatable..."
- Doofenshmirtz and his strange obsession with using Eulg (which destroys stickiness) on the Tri-State Adult Diaper Factory. It is, apparently, backstory worthy. Perry the Platypus chose, wisely perhaps, not to find out.
- Whatever happened when the Fireside Girls went to see what Baljeet is doing to earn a patch. It was rather implied that it was a bad decision.Holly: That patch wasn't worth it.
- They may have just been implying that Baljeet was doing some really boring scientific equations, like he usually does.
- Also from the same episode, whatever happened when Milly went back one afternoon after the other Fireside Girls went home.
- In "We Call It Maze" we hear the beginning of Doof's backstory:Doof: Ten years ago I was backpacking across Europe when I came across a group of Canadian college students. Dylan was the most popular among the group, but I was the oldest, so rivalry was inevitable...
"...then the ambassador's wife filed a complaint: long story short, I am never welcome in Albania ever again. But the point is I ended up alone in Italy..."
- But not the middle, just the end:
- Doof's actually full of these:Doof: (Upon seeing a dodo, expressing his disappointment) "... it looks like a turkey! It's like Thanksgiving! (the dodo starts attacking him and we hear, from off screen) Exactly like Thanksgiving!"
- From the episode featuring Paul the delivery guy, we get this one from Love Händel:Bobbi: "Hey guys, we're covered in juice and packing tape. What does that remind you of?"
Danny: Detroit, 1984. *Danny and Swampy high-five.*
- Similarly in the movie, when their bus gets knocked over by killer robots it's "Albuquerque '93 all over again."
- In "Lotsa Latkes" Candace explains why she can't hang out with her friends by saying Jeremy is working, Stacy is grounded and Jenny is protesting. We know where Jeremy works, but there's no explanation for why Stacy is grounded or what Jenny is protesting.
- "Norm Unleashed": Whatever Doofenshmirtz's Schmaltz-inator can be used for, it was something Dr. Diminutive was arrested for when he used the inator. Presumably it has something to do with either rendered poultry fat or excessive sentimentality.
- A brief moment near the end of "Perry the Actorpus" after Linda finishes playing bagpipes—remarkably well—for Lawrence (whose Celtic dance ends with an exploding flourish). With a palpable sense of relief, she says, "I guess that answered the inflatable legs question." Why they'd been alone in the attic needs no explanation.
- In "Ladies and Gentlemen, Meet Max Modem", Doof references what must have been a particularly nasty defeat that we're probably happier not having seen:Doof: "Mustn't forget to open the roof. A little something we learned from the 'Diarrhea-inator' debacle, right Perry the Platypus?"
- In "Mind Share," Buford says that every prison has a guy who knows how to get things:Baljeet: "How do you know what every prison...?"
Buford: "Ah! Don't go there!"
- In "Phineas and Ferb Save Summer:"Candace: "So, you guys didn't move the Earth out of orbit?"
Phineas: "Not this time, no."
- The time Candace got her head stuck in the sink.
- One can only wonder why Doofenshmirtz has a problem with underwater welders.
- The episode "The Chronicles of Meap" gives these rapid-fire: part of Dr. Doofensmirtz's backstory for that episode involved him not having friends as a kid because he smelled like pork all the time, because of another traumatizing back story that he didn't want to get into, which somehow. Though that incident may have been revealed later on: for a time, he operated a bratwurst stand, which would explain the pork smell. Also, somehow, he was disowned by his parents and raised by ocelots. How and why this happened (and how later episodes imply he went back to living with his parents for a short while) is left unexplained.
- Also strangely averted in the same episode, when Ferb drives the ride he'd earlier built across Danville - the speed he's going at causes it to rip off all of Baljeet's and Buford's clothes (save underwear), who were just passing by. After a beat, Buford comments "We must never speak of this again", to which Baljeet responds "Agreed".
- Lawrence's fishing stories from "The Lake Nose Monster" qualify, as well. The story about "the time [he] caught Big Mouth Ramone" provided us with this gem, at any rate: "...it was either back up the fire escape or lose the pants altogether..."
- And from the very first episode:Candace: Mom! You gotta come home, right now.
Linda: Did a satellite crash into the house?
Candace: No, no no. You gotta see what Phineas and Ferb are doing.
Linda: Seems like we had this conversation before.
Candace: What do you mean?
Linda: I seem to recall you telling me, that the boys were training monkeys to juggle bicycles. And when I come home, there was a stunning lack of monkeys.
Candace: I still don't know how they cleaned it up so fast.
- Actually, if one were to watch the extended pilot version of this episode, they were originally going to feature a scene, referencing to this joke and explaining everything.
- Of course, that implies that they've done crazy stuff like that before the beginning of this summer, but the Christmas special implies that their first project was the rollercoaster.
- If you haven't seen some of the featured clips in the second clip show, they can certainly feel like this, but in every flashback there's at least one featured that never really happened in the show— of particular note are "the Blow-itself-up-inator" and "I knew I should've gotten a down payment on that elephant."
- Played with in "Unfair Science Fair" and later subverted in "Unfair Science Fair (Redux)". At the end of the first, Isabella commented that Phineas and Ferb made a portal to Mars but didn't use it. She was then told that they DID use the portal but that was "another story". The later episode turned out to be the "another story".
- Candace wearing a tube top while feeding the geese also falls into this department.
- How Buford wound up on Candace's contact list in "The Lemonade Stand" is probably one of these.
- Candace wondering how or why she has a poster of a hypnotist in her room definitely counts.
- When Lawrence had a contest with his brother to see who could wear the most shirts at the same time, he loses, even though he's wearing so many shirts that it looks like he's in a fat suit. Linda comes over and says, "What's the matter, honey? I've seen you wear more shirts than that."
- This gem from "Where's Perry Pt. 1":Major Monogram: (After spotting a large box of straws) Hmm, that gives me an idea. And this time, a good idea. Not like the one I had about the- (scene change)
- Buford's goodbye words to a bunch of squirrels in "What'd I Miss?" probably qualifies:Good luck, little guys. I'll think of you whenever I get a rabies shot. Which is often.
- Dr. Doof mentions the nicknames he's given to various people, including calling Carl "Dr. Coconut" and mentioning "Sometimes I wish I didn't know so much." During the credits, we get to see why he calls him Dr. Coconut He dances to Hawaiian music while wearing a stethoscope, a grass skirt and a coconut bra, but we don't get to know just how Doof knows about it.
- Candace doesn't want to hear anybody mention that clothesline incident, in "Knot My Problem".
- In "Bee Story", Isabella is about to flashback to the Fireside Girls' unsuccessful first attempt at getting their beekeeping patches, but Gretchen interrupts her.
- In the movie, after Phineas finds out about Perry's secret agent job, he asks if anyone else has "a bizarre double life". Without looking, he tells Ferb to put his hand down. What are they referring to?
- Perhaps it was the same thing Ferb told Phineas off-screen in Spa Day, of which all we hear is Phineas telling Ferb Your secrets safe with me.
- Doofensmirtz's date who kept stabbing him with a fork mentioned in "Get That Bigfoot It If My Face"