Perry, Phineas, Ferb, Candace and Doofenshmirtz are about to be fed to a Goozim. Phineas tries to get a positive side about their situation. It all started that morning when he and Ferb celebrate five years since they adopted their pet platypus, Perry. They get dressed with help from Perry. After reminiscing about how they got him from the O.W.C.A.’s animal shelter, they decide to build a giant platypult to launch themselves off of. With the help of their friends Isabella, Buford and Baljeet, they launch themselves off of the tail of the Platypult 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 decides to grow up and act more like an adult. She and her friend Stacy go to the backyard to bust the boys, since, now that Candace is an “adult”, she can bust the boys herself. However, she finds that 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, and so kept her from seeing the boys' invention as well. 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 of his owners lest they find out his secret. They successfully 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, who has a scar that goes over his eyepatch. Dr. Doofenshmirtz is redirected by the 2nd Dimension Monogram to a ride that takes him straight to Doofenshmirtz-2. There, they meet.

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, General Platyborg, the 2nd Dimension Perry who was defeated and turned into an evil cyborg by Doofenshmirtz-2 a long time ago, to attack Perry, hoping that it will cause Perry to reveal that he is a secret agent. However, Perry remains in his mindless guise even after being hit. Doofenshmirtz-2 then tells Platyborg to hit the boys, to which Perry punches the Platyborg away and reveals his identity.

Phineas and Ferb are surprised at this, and hurt that Perry didn't tell them that he was an agent (primarily Phineas, who yells at Perry for not telling them). Doofenshmirtz-2 summons Norm Bots to seize the trio. The three fall through a window, but Agent P releases his parachute. They land on top of another building, where Agent P does combat against Platyborg with his feet stuck in a skull from an animal skeleton from Doofenshmirtz-2’s lair. Phineas and Ferb trap Platyborg in Agent P’s parachute. Phineas begins to express his anger at Perry again until he realizes that Perry is caught in the parachute. Phineas and Ferb try to pull him back up and they all end up being "saved by unconventional architecture". A Norm-bot approaches them as well as Platyborg, but the Norm-bot is hit by the skull and Platyborg is hit by a bus. Phineas, Ferb and Perry are then able to escape.

Act II Edit

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. As well, Phineas is trying to get over the fact Perry is a secret agent and wonders if Perry is family. Ferb assuages him, and the boys decide they need find their 2nd Dimension selves, who have never heard of summer before. Agent P, upon seeing a news report on TV saying that he should turn himself in to Doofenshmirtz-2 or else Doofenshmirtz-2 will hurt his friends, begins to leave, but is stopped by Phineas and Ferb.

Phineas disowns Perry, telling him to go ahead and go, as he can’t trust Perry anymore, and Agent P leaves. 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. It is revealed that Buford-2 was part of the The Resistance against Doofenshmirtz-2, but became so good at it that he started resisting the Resistance too. 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, Doofenshmirtz-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, along with Phineas-2 and Ferb-2, who have stowed away, go underground in mine carts to attempt to break into Doofenshmirtz-2’s lair and rescue Perry. But they find out that it is a trap, and they are captured.

Act III Edit

Doofenshmirtz-2 taunts Perry that he has captured him and his friends around 3:30 to 4 pm EST that Perry remembers and presses a button on his watch, which opens up a hologram of Major Monogram, who, at that moment, is in the shower. The Doofenshmirtzes, Platyborg 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 back. Meanwhile, Phineas and Ferb refuse to fix the Other Dimension-inator, but Doofenshmirtz remembers the boys removed his self-destruct button, repairing the device. Now obselete, Doofenschmirtz sentences the four to doom, as well as regular Doofenshmirtz, as he had gotten on Doofenshmirtz-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 (thanks to Doofenshmirtz's poor climbing skills), 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. When he realizes what it is, he tells Perry to let go of the Goozim's cage, but he hesitates. Phineas pleads with Perry to trust him, and he lets go of the cage, just as Phineas 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, so Phineas closes the portal. Candace-2 is captured, and Doofenshmirtz-2, though enraged, goes on with the invasion of the 1st Dimension Tri-State Area. The group goes through numerous dimensions with the Norm Bots in pursuit.

Act IV Edit

As Buford, Baljeet and Isabella are talking in the park, Phineas, Ferb Candace, Perry and Doofenshmirtz manage to get back in the 1st Dimension. At the same time, however, Doofenshmirtz-2 arrives on Doofenshmirtz Evil Incorporated, retracts the roof as the Other Dimension-inator rises up and activates a portal, allowing millions of Norm-Bots to invade Danville. 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, activated by the locket, saying that, in desperate times such as these, Agent P needs their help, and that he knows they can help him because of their Big Ideas. Many of Phineas and Ferb’s inventions from past episodes of the series are recreated, and the kids from Danville take control of them, managing to save the agents, who were surrounded by the Normbots, and go to war with the Norm Bots. In the heat of battle, Phineas and Perry get to the top of Doofenshmirtz Evil Incorporated building, where they find Doofenshmirtz-2 sending off more of his robots. Perry fights Platyborg, while Phineas goes head-to-head with Doofenshmirtz-2, after he is caught trying to disable the portal.

Perry is eventually able to defeat Platyborg, who, with a chicken stuck on his head and corn in his hands, gets his tail stuck in an electrical socket and is electrocuted. Phineas realizes the dish is what controls the robots, so he goes for the baseball launcher, which Doofenshmirtz-2 grabs and is subsequently cornered by Doofenshmirtz-2, who aims at him with the baseball launcher. Perry hands Phineas a baseball bat, which he uses to hit the baseball that Doofenshmirtz-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 plungers, reaches his brother and pet. An enraged Doofenshmirtz-2 emerges from the ground in the cockpit (sleeve) of a 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. Doofenshmirtz-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, Doofenshmirtz-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 is going on in hopes that the mysterious force will make it disappear. Doofenshmirtz-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, something she takes pride in.

Doofenshmirtz-2 returns to the 2nd Dimension, where he is arrested by Monogram-2 and the Firestorm Girls. 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 (Doofenshmirtz tied up for some reason) 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, and seemingly somewhat pleased at this, but before he can stop him, 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. He smiles, saves the pictures, and the movie ends.

Act IIEdit

Act IIIEdit

Act IVEdit

Act II Edit

Act III Edit

Act IV Edit