Phineas and Ferb The Movie: Across the 2nd Dimension (alternate titles: Phineas and Ferb: The Movie, Phineas and Ferb: Across the 2nd Dimension and Phineas and Ferb: Across the 2nd Dimension in Fabulous 2D!) is a Disney Channel Original Movie, and the first film of the Phineas and Ferb franchise. It premiered August 5, 2011, and was first mentioned by Jeff "Swampy" Marsh in an interview with the Daily Telegraph in 2010.  
It's been five years since Phineas and Ferb adopted their pet platypus, Perry from the O.W.C.A.'s animal shelter. To celebrate, they and their friends play giant platypus badminton. Phineas and Ferb are launched off of a giant platy-pult in a shuttlecock, and end up crashing on the roof of Doofenshmirtz Evil Incorporated, destroying the latest invention of Dr. Doofenshmirtz, the Other Dimension-inator.
Feeling sorry for him, and not knowing that he is evil, the boys help him rebuild it, and they successfully create a portal to the 2nd Dimension. There, they discover that the 2nd Dimension's Tri-State Area is ruled by a much more evil and sinister Doofenshmirtz. The boys meet their alternate selves, find out that Perry is a secret agent, and team up with a group of civilians dubbed The Resistance to end Doofenshmirtz-2's reign and save the world.
It’s been 5 years since Phineas Flynn and Ferb Fletcher adopted their pet platypus, Perry. After singing “Everything's Better with Perry”, and reminiscing about how they got him from the O.W.C.A.’s animal shelter, they decide to build a giant platy-pult to launch themselves off of. With the help of their friends Isabella Garcia-Shapiro, Buford Van Stomm, Baljeet, they launch themselves off of the tale of the platy-pult in a large shuttlecock, and fly through the air. Perry, who has assumed his secret agent role as Agent P, has returned from a mission briefing with Major Monogram and Carl, the latter who has given him several new gadgets. While riding in his new rocket car, Agent P collides with Phineas and Ferb’s shuttlecock, and they crash on the roof of the Doofenshmirtz Evil Incorporated headquarters, destroying Dr. Doofenshmirtz’s latest invention, the Other Dimension-inator.
Meanwhile, after learning that her boyfriend, Jeremy, is looking for colleges, Candace Flynn decides to grow up and act more like an adult. She and her friend Stacy Hirano go to the backyard to bust the boys, since, now that Candace is an “adult”, she can bust the boys herself. However, she finds her brothers and the platy-pult are gone, with only Isabella and Baljeet remaining. Candace concludes that the Mysterious Force, the force that she believes takes away Phineas and Ferb’s invention before her mother can see them, recognizes Candace as an adult. She and the rest of the group go to the park to look for the boys.
Feeling sorry for him, and not knowing that he is evil, Phineas and Ferb help Dr. Doofenshmirtz rebuild his Other Dimension-inator, much to the horror of Perry, who must pretend to be a mindless pet in the vicinity pf his owners lest they find out his secret. They succeesfully open a portal to the 2nd Dimension and step through it. They find that that the Tri-State Area in this dimension has been taken over by the 2nd Dimension Doofenshmirtz. Dr. Doofenshmirtz is redirected by the 2nd Dimension Monogram to a ride that takes him straight to Doofenshmirtz-2. There, they meet and sing “A Brand New Best Friend (and It's Me).Phineas, Ferb, and Perry follow, and Doofenshmirtz-2 recognizes their pet as Perry the Platypus, while the regular Doofenshmirtz doesn’t. Doofenshmirtz-2 sends his minion, Platyborg, who is the 2nd Dimension Perry who was defeated and turned into a cyborg by Doof-2 a long time ago, to battle Perry. Perry remains mindless even after being kicked. Doof-2 tells Platyborg to hit the boys, to which Perry reveals his identity and punches the Platyborg away.
Phineas and Ferb are surprised at this. Doof-2 summons Norm Bots to seize the trio. The three escape, and fall onto the side of the building, with Agent P doing combat against Platyborg with his feet stuck in a skull from a skeleton from Doof-2’s lair. Phineas and Ferb trap Platyborg in Agent P’s parachute, which had been deployed when the three fell down the building. They are able to escape. Back in Danville, Candace, Stacy, Isabella, and Baljeet have found Buford in the park chewing Victory Gum, as he had won the platypus badminton game they were playing earlier, even though it was more of a forfeited win since Phineas and Ferb had gone missing.
In the 2nd Dimension, Phineas and Ferb try to use a remote version of the Other Dimension-inator to get home, but it just opens a portal to another dimension they don’t know. They find their 2nd Dimension selves, who have never heard of summer before. To explain, they sing “Summer (Where Do We Begin?).” Agent P, upon seeing a news report on TV saying that he should turn himself in to Doof-2 so he won’t hurt his friends,begins to leave, but is stopped by Phineas and Ferb.
Phineas tells him to, as he can’t trust him anymore, and Agent P goes, as “I Walk Away” plays. Afterward, they attempt to go across the street to Isabella’s house, but are stopped by a lone Norm Bot, who is taken down by the 2nd Dimension Buford. The five fall down a chute once entering Isabella’s yard, and end up being tied by the Firestorm girls, the 2nd Dimension versions of the Fireside Girls. They are interrogated by the 2nd Dimension Isabella, to which Phineas replies that they are Candace’s brothers. They are untied and led to 2nd Dimension Baljeet, who prefers to be called “Dr. Baljeet.” He explains that the 1st Dimension and the 2nd Dimension are right next to each other, but to get to the 1st Dimension, they would need a lot of energy. 2nd Dimension Candace, who is the leader of the Resistance, shows up, and commands everyone to begin work.
Meanwhile, Doof-2 has decided to go the 1st Dimension’s Tri-State Area to conquer there. He gets regular Doofenshmirtz to create another Other Dimension-inator, but it fails to work. It seems that they will need the boys’ help to make it. Dr. Baljeet has been able to open a portal to the 1st Dimension. Upon seeing a news report that Perry has been captured, Phineas and Ferb want to rescue him. Meanwhile, Candace and Stacy are in the Flynn-Fletcher backyard, and Candace tries to talk to the Mysterious Force. The portal from the 2nd Dimension opens up, which the two girls believe is the Force. Candace goes through, causing the portal to close, and her being stuck with the 2nd Dimension gang.
Phineas, Ferb, Candace, Candace-2, Buford-2, Isabella-2, Buford-2, and Phineas-2 and Ferb-2 who have stowed away, go underground in mine carts to attempt to break into Doof-2’s lair and rescue Perry. But they find out that it is a trap, and they are captured. Perry presses a button on his watch, which opens up a hologram of Major Monogram, who, at that moment, is in the shower. The Doofenshmirtzes and the Norm Bots look away in disgust, and the kids are able to escape. The group tries to race away in the mine carts as the Norm Bots pursue them. To save her and her brothers, Candace-2 separates the mine carts, and she and the rest of the Resistance are able to escape, while Phineas, Ferb, Candace, and Agent P are seized.
Back in Danville, Stacy builds a shrine to the Mysterious Force as an apology for not believing in it, in hopes that it will bring her friends. Meanwhile, Phineas and Ferb refuse to fix the Other Dimension-inator, so he sentences the four to doom, as well as regular Doofenshmirtz, as he had gotten on Doof-2’s nerves. The group, in chains, is led to a caged Goozim. Perry is able to get keys to unchain the gang, but the Goozim’s movements toss them around, and the keys drop near the lava that takes up the ground. As the gang nearly dangles near the magma, Candace is able to catch the keys. Suddenly, Candace-2 shows up with the Other Dimension-inator remote. She defeats the surrounding Norm Bots, and throws it to Phineas, who opens a portal to another dimension. The group falls through a portal to a flower dimension, and they use the keys to unchain themselves.
The portal is still open, however, so the Norm Bots come through it. Phineas closes the portal. Candace-2 is captured, and Doof-2, though enraged, goes on with the invasion of the 1st Dimension Tri-State Area. The group goes through numerous dimensions as “Brand New Reality” plays, with the Norm Bots in pursuit. Eventually, they end up back in the 1st Dimension.
Candace-2 who has been imprisoned, is rescued by the 2nd Dimension Jeremy, and Phineas-2 and Ferb-2, who have taken on new clothing. After hugging her brothers, Candace tells the 3 of them to go with her to help stop Doofenshmirtz-2 from taking over the 1st Dimension, and they all leave.
Agent P is told by Major Monogram to assist the other agents in fighting the invading robots, while Phineas, Ferb, and Candace are simply told to go home. There, Perry’s locket, which Phineas has, beeps, leading them to Agent P’s lair. They receive a message, saying that, in desperate times such as these, Agent P needs their help. Many of Phineas and Ferb’s inventions from past episodes of the series are recreated, and the kids from Danville take control of them, and go to war with the Norm Bots, as Love Handel sings “Robot Riot.” In the heat of battle, Phineas and Perry get to the top of Doofenshmirtz Evil Incorporated building, where they find Doof-2 sending off more of his robots. Perry fights Platyborg, while Phineas goes head-to-head with Doof-2.
Perry is eventually able to defeat Platyborg, who gets his tail stuck in an electrical socket and is electrocuted. Phineas is cornered by Doof-2, who aims at him with a baseball launcher. Perry hands Phineas a baseball bat, which he uses to hit the baseball that Doof-2 shoots at him from the launcher. The baseball hits the satellite which controls the Norm Bots, and they all fall to the ground, deactivated. Ferb, who has been climbing up the side of the building with plumbers, reaches his brother and pet. Doofenshmirtz-2 emerges from the ground with a giant robot version of himself and goes to smash Phineas, Ferb, and Perry.
At that moment, Doofenshmirtz, who left his keys in the 2nd Dimension and has been trying to get his neighbor Mrs. Thompson to let him into the building, shows up, and unveils his toy train from his childhood, Choo Choo. Doof-2 had lost his toy train when he was a child, and that’s what had caused him to go evil and takes over the 2nd Dimension Tri-State Area. Once he sees his lost train, Doof-2 climbs down the robot, and embraces the toy.
Meanwhile, Candace, who has given up on becoming an adult, goes to the movie theater, where her parents Linda and Lawrence, have been. She tries to get her mom to go outside with her to see the grand battle that it Is going on outsid. Doof-2, who has now become less evil, apologizes for his wrong-doings, and reveals that he has had Self-Destruct buttons on his Norm Bots after all. He presses a button on a remote, and all the robots in the Tri-State Area blow up and disappear. Candace and Linda get outside, and find that all the robots have vanished, and that Candace has failed at busting her brothers – again.
Doof-2 returns to the 2nd Dimension, where he is arrested. The Resistance enters Danville, and thanks Phineas, Ferb, and Candace for all they’ve done. The Platyborg has had the evil “fried” out of him, and Phineas-2 and Ferb-2 rush to hug him, happy that their pet has returned. After the 2nd Dimension characters leave, Monogram and Carl show up, and tell Phineas and Ferb that Perry has to go away forever due to his secret being blown. The boys ask if there’s something else they can do to keep their pet, and Monogram and Carl remember that Doofenshmirtz built an Amnesia-inator, and that if they can power it up, they can wipe the gang’s memory of that whole day (including learning Perry’s identity as Agent P) so they can keep him.
Back at the O.W.C.A.’s headquarters, Phineas, Ferb, Candace, Jeremy, Buford, Isabella, Baljeet and others are lined up to get their memories erased. The brothers say their last good-byes to Agent P. Isabella kisses Phineas, finally being able to live out her fantasy. Phineas is surprised at this, but before he can say any more, Carl fires the Amnesia-inator. Later, Agent P enters his lair, and plugs his camera into the screen, and watches photos taken of he and his owners during their adventure as “Takin' Care of Things” plays. He smiles, and the film ends.
During the end credits, the music video for Kick It Up a Notch is scene (with the live-action opening cut out) is seen on the left side, with the actual credits on the right. After the credits end, the ending of the music video takes up the whole screen. The logos for "Walt Disney Television Animation" and "Disney Channel" are seen.
- Everything's Better with Perry
- A Brand New Best Friend (and It's Me)
- Summer (Where Do We Begin?)
- I Walk Away
- Brand New Reality
- Robot Riot
- Takin' Care of Things
- Kick It Up a Notch (credits)
- Mysterious Force (Cut song)
- Danza Kuduro (credits - Dutch)
The "Too Young" Line
Phineas: (To Perry) Of course, Ferb and I knew exactly what to call you.
Young Phineas and Ferb: Bartholemew.
Phineas: (To Perry) So, not only have you been leading a double life this whole time, but you sat there and let us help an evil scientist open an evil portal into an evil dimension. And you did nothing to stop us?
Ferb: Well, he did pee on the couch.
Ferb: ♪ It's noticeably warmer ♪
NOTE: This line is also repeated by Ferb-2 later in the song.
Phineas: You know, I used to think you couldn't spell "platypus" without "us".
Ferb: Well, you could, but it would just be Platyp.
Ferb: Whoa. Deja-vu-ish.
Ferb: Well, we've had a lot of great days, but we only have one Perry.
Isabella: Hey Phineas! Whatcha doin'?
Phineas: Turning Perry's involuntary reflex into a sporting event.
Isabella-2: Whatcha doin'?
Phineas: Hey where's Perry?
Phineas: Hey, where's Dr. D?
Perry's Lair Entrance
A tube behind a painting, he lifts it and gets sucked in, Perry ends up being in a tube elevator and riding down to his lair.
Doofenshmirtz Evil Incorporated!, Doofenshmirtz Evil News Broadcast!, ;;Doofenshmirtz Evil News Update!
- The movie was shown at select movie theater screenings, and at Comic-Con 2011. As well, the movie premiered on Disney on Demand on August 1st, 2011 August 5th on Disney Channel, August 13th on Disney XD, August 20th on ABC, and will be shown starting August 18th on the Disney Cruise Line.
- The movie is in theaters in Belgium, the Netherlands, and Spain.
- The film's first trailer was attached to the DVD release of The Sorceror's Apprentice. It was a teaser, and contained no new footage. On June 7th, the official trailer was released, revealing the release date of August 5th.
- The original title was Phineas and Ferb: Across the 2nd Dimension in Fabulous 2D. Creators Dan & Swampy have said that they wanted 2D glasses to be distributed for viewers to get the full 2D effect of the movie, but the plan fell through. 
The film's initial reviews are generally positive. Matt Blum of the Wired.com website claims that "this is truly an instant classic, right up there with some of the best cartoons ever made". Los Angeles Times Television Critic Robert Lloyd enjoyed Phineas and Ferb: Across the 2nd Dimension as well, noting "a hint of emotional depth, regarding the love between animals and the people who live with them". Both reviewers highlighted the film's employment of adult-oriented humour that makes it equally enjoyable for viewers of all ages. Cartoonclack praised that the TV movie based on a kid’s cartoon can be smart, entertaining, and, dare I say it … moving."
The film averages 7.6 million viewers, the movie soared to become TV’s No. 1 scripted telecast of 2011 to date among Kids 6-11 (3.4 million/13.8 rating), TV’s No. 1 movie among Tweens 9-14 (2.6 million/10.8 rating) and cable’s No. 1 movie of the year in Total Viewers.
Moreover, the movie ranked as cable’s No. 1 animated telecast in more than 3 years among Kids 6-11 and Tweens 9-14, and ranks No. 4 among all animated cable telecasts in the Tween demo. On IMDB, the film has an 8.8 user rating with 216 votes,  which would be good for no worse than 15th for all movies, no worse than 5th among adventure movies, the top animated film all-time,  and no worse than 2nd for family films and film made in the 2010s.
- Review: Phineas and Ferb: Across the 2nd Dimension Is an Instant Classic
- TV review: 'Phineas and Ferb The Movie: Across the 2nd Dimension'
- Phineas and Ferb: Across the 2nd Dimension does it right – CartoonClack
- "Phineas and Ferb: Across the 2nd Dimension" Averages 7.6 Million Total Viewers By Robert Seidman – August 6, 2011