Phineas and Ferb the Movie: Across the 2nd Dimension is a 2011 American animated science fantasy action-adventure comedy-drama television film based on the American animated TV series Phineas and Ferb. The film premiered on August 5, 2011 in the United States.^[1][2] It was first announced by Jeff "Swampy" Marsh during a January 2010 interview with the Daily Telegraph.^[3] The events of the film take place during the third season of Phineas and Ferb. It is the first feature-length film of the Phineas and Ferb series, and the third animated Disney Channel Original Movie, following Kim Possible Movie: So the Drama and The Proud Family Movie.

The film's premiere averaged 7.6 million viewers, making it one of the highest-rated animated programs on cable in more than three years. It later gained over 3 million viewers to become the second most watched animated basic cable telecast ever among kids 6–11 and teens 9–14, and cable's fifth highest viewership movie ever in total viewers.^[4] A standalone sequel, Phineas and Ferb the Movie: Candace Against the Universe, was released on August 28, 2020 on Disney+.

To celebrate the anniversary of Perry becoming their pet, Phineas and Ferb create an enormous shuttlecock to play giant badminton. When Perry's hovercraft accidentally collides with their shuttlecock, the boys crash into Dr. Doofenshmirtz's lab and destroy his "Other-Dimension-inator", which creates portals to parallel dimensions. Intrigued, the two help Doofenshmirtz rebuild the machine. Perry arrives to stop Doofenshmirtz, but unwilling to reveal his secret identity to the boys, reverts to pet mode and is unable to stop them from helping Doofenshmirtz.

The group travels to an alternate dimension where an evil Doofenshmirtz rules the Tri-State Area with his army of Norm-Bots. The second Perry (known as Platyborg) was converted into an evil cyborg by Doofenshimrtz-2 and programmed to serve as his second-in-command. Doof-2 orders Platyborg to attack the boys, forcing Perry to reveal his secret identity, much to the boys' shock. Perry and the boys escape, but Phineas and Ferb are angry with Perry for his long term deception.

With the remote for their portal broken, the boys seek out their alternate selves, who have grown up without knowing about summer. Doofenshmirtz-2 decides to use the Other-Dimension-Inator to invade the original Tri-State Area. In order to keep Perry off the track, Doof-2 announces he will spare Phineas and Ferb if Perry surrenders. Perry agrees to the deal, but before he leaves is told by an angry Phineas and Ferb that he is no longer their pet. When Doofenshmirtz-2 learns that only the boys can fix the Other-Dimension-inator, he reneges on the deal.

Phineas and Ferb ask the alternate Isabella for help and find that she and alternate versions of Baljeet, Buford, and the Fireside Girls are part of the resistance movement, led by the alternate Candace. Baljeet-2 is able to open the portal to the original dimension, but upon learning about Perry's capture, Phineas and Ferb decide to rescue Perry before they can leave. In the original dimension, Candace spots the portal and jumps through, causing it to close.

The kids set off to rescue Perry, but are trapped by Doofenshmirtz-2 and his forces. They escape with Perry when he provides a distraction, but during the chase, Platyborg disables one of the mine carts, slowing them down. Unwilling to endanger her brothers, Candance-2 abandons Phineas, Ferb, Candace-1, and Perry. The boys refuse to fix the machine, but inadvertently remind Doofenshmirtz how they fixed his machine by removing the self-destruct button. After Doofenshmirtz powers up the machine, Doofenshmirtz-2 orders Phineas, Ferb, Candace, and Perry to be fed to a monster called the Goozim; when Doofenshmirtz annoys him again, Doofenshmirtz-2 orders him to be fed as well.

Before the five can be eaten, Candace-2 rescues them and gives them the remote, allowing Phineas, Ferb, Candace, Perry, and Doofenshmirtz to travel through other dimensions until they reach their home dimension. Despite this Candace-2 is captured by the Norm Bots. Doofenshmirtz-2 arrives at their dimension and releases the Norm Bots into Danville. Perry gives Phineas and Ferb the locket off his collar, which leads them to Perry's lair. Inside, they find replicas of all their previous inventions. With the help of their friends, the children of Danville, and the O.W.C.A. agents, Phineas and Ferb use the inventions to defeat the Norm Bots, while Candace-2 is freed by Phineas-2, Ferb-2, and Jeremy-2, and Perry defeats Platyborg. Doofenshmirtz arrives and gives Doofenshmirtz-2 a toy train that he lost when he was a kid, which was the sole reason he turned evil. His tragic backstory resolved, Doofenshmirtz-2 self-destructs his Norm Bots and returns to his own dimension, only to be arrested.

Platyborg, freed from his evil programming, reverts to his normal self, and Phineas-2 and Ferb-2 take him home. The kids are distraught to learn that Perry will be relocated since his cover is blown, but Carl remembers Doofenshmirtz has an Amnesia-inator that can erase memories. Phineas, Ferb, Candace, and their friends have their memories erased, allowing them to keep Perry. Before they forget, Phineas and Ferb say their goodbyes to Perry, and Isabella seizes the opportunity to kiss Phineas. Perry enters his lair and uploads photos from the day onto his computer, smiling happily.

Olivia Olson was set to appear as Vanessa Doofenshmirtz and Vanessa-2, but her scenes were cut from the film.

The soundtrack album for Phineas and Ferb the Movie: Across the 2nd Dimension, including eight songs heard in the film and 14 songs from the series, was released on August 4, 2011. Guns N' Roses guitarist Slash co-wrote and performed a song for the soundtrack titled "Kick It Up a Notch", while the song "I Walk Away", which is heard in the film, is not included in the soundtrack. A song cut from the film, "Mysterious Force", is included.

Walmart sells a version of the soundtrack with 10 extra songs.^[5]

The DVD release includes eight scenes that were completed but cut out due to timing issues. The deleted scenes include:

• "Mysterious Force": Extended scene and included a song that was also cut from the final movie.
• "Pretendy the Practicepus (Extended)": Extended scene where Doofenshmirtz practices his speech with a toy Perry. Vanessa also appears in this scene.
• "2nd Dimension Vanessa": Vanessa-2 argues with her father over him constantly banishing any boy that talks to her.
• "2nd Dimension Flyover": The main characters ride in a blimp to the doom temple.
• "News Report": A news report detailing the incoming Doofenshmirtz-2 invasion.
• "Perry's Lair (Extended)": Extended scene from when the boys find Perry's lair.
• "Kick It Up a Notch (Extended)": Extended version of the final fight scene.
• "Ending Scene (Extended)": Extended scene of the characters getting their memory wiped. Has a gag where they need to redo the memory wipe after they see Perry in his agent persona.