Trivia / Phineas and Ferb The Movie: Across the 2nd Dimension
Actor Allusion: In the final battle, The Beak suit is piloted by Baljeet and Irving, the two characters voiced by actors from 30 Rock.
All There in the Manual: The official movie magazine features a comic showing how Doof 2 transformed Perry 2 into Platyborg, and took over his Tri-State Area, although its canonical status may be in question.
Cut Song: "Mysterious Force" was a song originally made for the movie, sung from Candace's point of view. Unfortunately, due to scaling back of the movie, it was scrapped. (It's on the soundtrack, if that means anything.)
No Export for You: While the US and other countries only have it on DVD, Japan got a Blu-Ray home release other countries don't have.
Non-Singing Voice: Ferb's lines in "Everything's Better with Perry" is noticeably more R&B than his normal British accent.
Talking to Himself: With most of the voice actors doing their original characters and their alternate universe counterparts, this will no doubt be inevitable.
Essentially all the deleted scenes. We not only have "Mysterious Force", but also Vanessa (from both dimensions) being in the film, an explanation for why the entire population of Danville didn't need their memories wipednote the robot invasion was passed off as a weather balloon, a longer (and rather heartwarming) version of the scene where Phineas and Ferb's inventions are replicated, and an extended "Robot Riot" (where we see Danny offhandedly tearing out a Normbot's CPU with his bare hand while singing about it). Considering that all the scenes were fully animated and presumably cut only due to time constraints, they are prime extended edition material
The Vanessa plotline in "Tales From the Second Dimension" follows up on her missing scenes.