* AlternativeCharacterInterpretation: Did Doofenshmirtz-2 really turn evil because he [[FreudianExcuse lost that toy train]]? Or did he have a past so unbelievably traumatic that he blocked it out, and funnels all those negative emotions into the loss of his beloved childhood toy? Or was he a horrible person [[EnfanteTerrible even as a kid]] and is just using the train as an excuse?
* BigLippedAlligatorMoment: "Brand New Best Friend", [[TropesAreNotBad as entertaining as it is]], is still a ''major'' BLAM.
* BrokenBase: While this is for the most part averted regarding the actual movie, [[StatusQuoIsGod the ending is a different matter...]].
* GeniusBonus: Or, perhaps, Liberal Arts Major Bonus - Norm's "Get me! I'm a Georgia O'Keeffe painting!"
** ''Ornithorhynchus anatinus'', the scientific name of the platypus, is among the lyrics of "Everything's Better with Perry".
** Existentialism trading cards!
*** "I'll trade you two Kafkas for a Dostoevsky." From Buford!
* HilariousInHindsight: For years, there have been tons of fan art and fan videos on YouTube showing Phineas and Isabella kissing. Then this movie comes and does it for real.
* MostWonderfulSound: Isabella finally planting one on Phineas.
** Unless, of course, you're [[MostAnnoyingSound NOT a Phinbella fan]].
** Then the sound of the Amensia-Inator hitting would a MostWonderfulSound, for those who aren't Phinabella fans.
* TheProblemWithLicensedGames: Quite successfully averted. The video game adaptation of this film is not only very enjoyable to play, but also has all the original voice actors, humor that could have come straight out of the show itself, and a [[AwesomeMusic seriously cool song to go with it]].
* TheyWastedAPerfectlyGoodPlot: What? No Vanessa (Original and Parallel) and/or Parallel Stacy? No Parallel Stacy is even more of one when you realize that [[spoiler:her absence is justified since Parallel Candace's "growing up" so fast probably made it so that she never met her world's Stacy, which makes the plot an even bigger waste because Original Candace and Stacy never bring that up or reflect on it.]]
** In a way, they already used that plot with Parallel Jeremy (While she ''did'' meet him, she thought of him purely as a soldier, rather than a possible friend or boyfriend like she would have had she not had to grow up so fast.) Throwing in the same thing with Stacy would have wasted time without adding much.
** And there ''was'' going to be a few scenes with both original and parallel Vanessa, but they had to cut them out due to timing. You can watch said deleted scenes on the DVD.
* WhatAnIdiot: Our Doof once built an army of robots just like Doof-2, except he 1) installed self-destruct switches and 2) placed them on the bottom of their feet so no one would be able to reach them. One step later and...