Phineas and Ferb try to make Isabella the biggest ice-cream sundae ever made after she gets her tonsils out.

Meanwhile, Dr. Doofenshmirtz attempts to create a space laser to destroy the annoyances that make his skin crawl. At the same time, Vanessa attempts to show her mother, Charlene, her father's evil schemes.
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!!Tropes
* BorrowedCatchphrase: When Phineas and Ferb check on Isabella after her tonsillectomy, Phineas borrows her catchphrase "What'cha dooooin?"
* TheCameo: The doctor checking on Isabella at the start is Stacy's mother, Dr. Hirano.
* ContinuityNod:
** Phineas points out that Candace is usually only in charge in case a satellite falls on the house, in a nod to "Rollercoaster".
** Doofenshmirtz's view is blocked by a sign advertising the "Brick" toy from "Toy to the World".
* CrushFilter: When Vanessa sees Ferb at Blueprint Heaven, she just flatly asks him, "Hey, how's it goin'?" When Phineas asks Ferb what went wrong, we see the same scene from his point of view, as Vanessa tussles her hair in the HotWind and is surrounded by flowers and smiles when she says, "Hey! How's it goin'?"
* DistantDuet: For the song "Busted", Candace and Vanessa as they work to bust their relatives.
* DistractedByTheSexy: Ferb accidentally switched the blueprints because he got distracted by Vanessa at Blueprint Heaven.
-->'''Ferb:''' I was weak.
* EarlyInstallmentWeirdness: Vanessa tries to bust Doof by showing his evil schemes to Charlene. Their relationship gradually improves into a semi-strained, but loving one.
* FailedASpotCheck: Both Linda and Candace failed to notice the laser attachment for the Space Laser-Inator (assuming that Phineas and Ferb hadn't gotten rid of it by then).
* GiantFood: Phineas and Ferb ''attempted'' to make a giant sundae for Isabella.
* LatexPerfection: The lady at the blueprint shop turns out to be Carl in a costume.
* MouthCam: Used at the beginning of the episode when Isabella is opening her mouth.
* ObfuscatingStupidity: Perry uses this to his advantage by pretending to be a normal platypus after being trapped by Doof inside a cage, so that Charlene sets him free out of pity.
* PhonyDegree: Vanessa questions her dad calling himself "Dr.", to which Doof shows Vanessa his diploma, with the price tag still left hanging.
-->'''Doofenshmirtz:''' They don't just give these out to anybody, you know.\\
'''Vanessa:''' Anybody with 15 bucks, they do.
* PrecociousCrush: This is where Ferb is first shown having a crush on Vanessa.
* SpellingSong:
-->''And I don't care what you've heard''\\
'''Cuz there's one six-letter word''\\
''It's gonna set me free (Gonna set me free)''\\
''Starts with a "B" (Starts with a "B")''\\
''It goes B-U-S-T-E-D, you are busted!''[[note]]Wait. Wouldn't that be "bustedur"?[[/note]]
* ScriptSwap: The blueprints for Phineas and Ferb's sundae machine and Doofenshmirtz's Space-Laser-Inator were accidentally switched at the blueprint shop, with none of them having a clue that they're building each other's plans as they follow along with the blueprints they got.
* StrangeMindsThinkAlike: Both Phineas and Doofenshmirtz utter, "Well, this can't be right," when they discover they got the wrong blueprints and built what the opposite wanted to make.
* TakeThat: During Doof's ImagineSpot, after the morning talk show host is disintegrated, there's [[AndThereWasMuchRejoicing some off-screen cheering]].
* TheTonsillitisEpisode: The episode starts with Isabella having recently had surgery on her tonsils, and Phineas and Ferb deciding to make her the world's largest sundae.
* WhatHappenedToTheMouse: The Space Laser-Inator Phineas and Ferb made blasted off, but the laser attachment was still left in the yard.