|“||Since it's our last day of summer, we're thinking a grand finale is in order!||”|
— Phineas Flynn
Candace wakes up just in time to hear her brother say his catch phrase and shouts to the gang that she intends to bust them once and for all. Candace is especially determined to bust them since this is the final day of summer vacation, but she trips on a roller skate, and a skateboard, and rolls down the stairs and lands into a wagon. Linda and Lawrence read the newspaper about a new tiger habitat at the Danville Zoo. Candace wheels into the dining room to hear that Linda has to do some errands to get ready for school resuming the following day.
In the backyard, Phineas and the gang determine to do something big since they have one more chance to find a good way to spend summer vacation. Phineas shows the gang a massive blueprint. Buford then wonders where Perry is.
Agent P enters his lair the very same way he entered it on the first day of summer. He enters his lair to discover that Carl already left for college, so Major Monogram has to do his own inserts manually. Monogram tells Agent P that he suspects Doofenshmirtz will do one last big evil scheme to take over the Tri-State Area. The manual inserts come apart and Monogram lashes out at Carl, only to remember that he's already heading for school. As Monogram mopes over Carl's absence, Agent P goes straight to his mission.
At Doofenshmirtz Evil Incorporated, Doof wakes up in his bed but hits his head on the lamp, which he disintegrates. Norm comes in to give him some chocolate cake for breakfast, much to his annoyance. He gets out of bed to see Vanessa coming to talk to him, but Doof does not have the time since he has a big to-do list, so Vanessa leaves him alone.
Back in the backyard, Phineas reveals the big idea, a giant, enormous tribute to every single thing they did over the summer. Buford wonders if it really is worthy of a grand finale. Phineas suggests they make sure that they hit the mark. Buford at first suggests they focus test it, but Phineas suggests they ride it. The gang rides on the contraption, which encompasses various fun and surreal things. Candace walks out and calls her mom. Baljeet reveals the reaction to the ride is almost unanimous, but Buford suggests some improvements. Phineas decides to go back to the drawing board, so Ferb transforms the ride into a drawing board. Candace and Linda come into the yard just in time to see nothing there and for Candace to once again "but but but". Candace decides to return some DVDs she borrowed from Vanessa.
Agent P arrives at DEI and immediately gets trapped in the bass drum of Norm's drumset. Doofenshmirtz explains to his nemesis that he realized that his goal of ruling the Tri-State Area was all for naught since it turned out there was no such position. So he unveils his newest inator, the Tri-Governor-inator, which will make him "Tri-Governor", a term he made up to mean the Ruler of the Tri-State Area. Perry escapes from his trap and fights Doofenshmirtz, but then the doorbell rings. Vanessa answers it to see Candace at the door. Upon seeing this, Perry runs and hides, as he doesn't want his cover to be blown. Candace returns the DVDs and vents to her about her failed busting attempt. Candace walks into the lair while Vanessa gets some tea. Candace then talks to Doof about her failure to bust her brothers, but Doof does not listen since he is looking for his nemesis. Candace then sits on one of Doof's inators, which he gets her off of. Doof explains that it is the Do-Over-inator, which is able to do the day over again through a time loop. Candace is intrigued by this and believes that she might have a chance of busting her brothers. Without hesistatation, Candace activates the -inator, and a bubble appears surrounding herself and Doofenshmirtz.
Suddenly, Candace finds herself back in her bed waking up to her alarm clock. When Phineas tells her that it is the last day of summer, Candace is elated to have one more chance to bust her brothers, but, once again, she slips and falls down the stairs. She finds herself reciting along with her parents, but they laugh it off as a philosophical thing.
Meanwhile, Doof also finds himself back in his own bed, confused why the lamp is back and Norm is once again offering him chocolate cake for breakfast. When he gets out of bed and sees Vanessa in the hallway again, he realizes the Do-Over-inator worked and he has a chance to improve his traps. But Vanessa is aggravated that her father is not listening and tells him she is permanently moving to her mother's.
Upon hearing of Vanessa's last words being recorded by Norm, Doofenshmirtz jumps to the conclusion that Vanessa is moving out simply because she thinks he is a loser. He figures that if he finally becomes the Tri-Governor, he can get Vanessa to move in with him.
Candace walks into the backyard when they gang reveal the blueprints and tells them this time that she will get her mom instead of calling her. After hearing Candace refer to the invention as "sky-high", Phineas gets an idea on how to improve it.
Perry gets trapped in the bass drum again, only this time, he rolls past Norm's drum set, escapes, and gets trapped in a giant skull. Perry escapes that trap as well and immediately hits the self-destruct button on the Tri-Governor-inator. Despite this, Doof states that as long as the Do-Over-Inator is activated, he will still find a way to defeat Perry.
Candace once again brings her mom to the backyard, only to discover once again there is truly nothing there. Once she leaves, it is revealed that Phineas and the gang decided to levitate the invention.
Candace wakes up from her bed a third time and realizes the day is once again repeating itself. This time, she attempts to avoid the roller skate, but still manages to slip onto a third roller skate and once again fall down the stairs. This time, Candace practically pushes her mom out the door.
Doofenshmirtz once again wakes up, but this time, he avoids the lamp. He tells Norm to "stuff it", so Norm eats the cake himself. Vanessa once again tries to talk to her father, but he too busy once again making improvements to his traps.
After Perry gets trapped in an escapes the skull, he gets trapped in a metal box, and Doofenshmirtz encases himself in a giant hamster ball. Perry escapes the trap and rolls Doofenshmirtz around the room. Norm offers some muffins, but they suddenly disappear into thin air.
Candace once again wakes up, and this time avoids all the things with wheels and once again pushes her mom out the door. As soon as she leaves, the spoon that Lawrence was eating cereal with disappears just like the muffins. Lawrence shrugs it off and laps at his cereal like a dog.
When Candace enters the backyard, she tells the gang she is going to bust them "out of this world", which brings further inspiration. During a montage, we see the various other ways both Candace fails to bust her brothers and Doof fails to trap Perry, each one weirder than the last.
After 23 loops, Doofenshmirtz ensures that he finally perfected his trap. He asks Norm for some muffins, but Norm is confused because he does not know what a muffin is, which made Doof realize that the effects of the Do-Over-inator creating time rifts in the space-time continuum that can erase anything from existence. After Perry is finally trapped, Doof fires his inator at City Hall, which replaces the dome with a Tri-Governor's Mansion. Doof then proceeds to get the citizens to vote for him as Tri-Governor.
Candace once again walks into the kitchen but then notices her parents both lapping at their cereals. She discovers that they do not know what a spoon is nor what tigers are. Things get even stranger when she notices her mother wearing green cargo shorts in place of her normal Capri pants. Candace then starts to suspect that something is going very wrong.
Meanwhile, Doofenshmirtz talks to Vanessa about her intent to move out and shows her the news of himself being elected as the new Tri-Governor, much to the horror of his younger brother Mayor Roger. A victorious Doof assumes that his daughter will want to live with him now that he has finally succeeded in his goal, but Vanessa isn't impressed by this. She tries to tell that what he assumes isn't the case, but she is interrupted when Doof runs off to turn off the Do-Over-inator to ensure that there won't be any more loops. However, a time rift sucks up the Do-Over-inator, so Doof assumes that since there is already erased from existence, there will be no more loops. He proceeds to move in to the Tri-Governor's Mansion with an unhappy Vanessa.
Candace runs to the backyard and asks her brothers to help her. She explains that she activated the -inator and days are repeating and things are disappearing. However, another rift appears and suck her brothers, much to Candace's dismay. She goes to her mom to tell her what happened, but Linda is confused because she has not heard of anyone named "Phineas" or "Ferb". Horrified to see that her mother doesn't even remember having two sons, Candace tries to explain the situation to Linda, but the latter is still very confused, much to Candace's frustration.
Meanwhile, in the Tri-Governor's Mansion, Doofenshmirtz proudly shows Vanessa her own suite as the First Daughter. Though Vanessa is somewhat impressed by the new features of the room, she tries to tell something important to her father, but Melanie comes in to tell Doof that he has a lot of things to do as the new Tri-Governor.
In a rather gray and colorless void that resembles Danville, Phineas and Ferb are wandering around and taking in their surroundings. They suddenly discover the things that disappeared, including spoons and Capri pants. They then see oranges coming down from the sky and hear something roaring in the distance, presumably tigers.
Candace goes to Isabella's backyard to see that the gang still know each other, but can't stand each other. Buford and Baljeet have no idea who Candace is and Isabella thinks she is an only child. Candace then tries to explain the situation to the gang, but they are unperturbed by this.
In his office, Doofenshmirtz awaits the arrival of an angry Perry. Doof reveals that he has put up and signed a legislation that makes it illegal for Perry and the rest of O.W.C.A. to interfere and thwart his future schemes until his term is over, and that it's been declared legal. Realizing that he can no longer thwart Doof anymore, a depressed Perry concedes defeat and is forced to leave by Doof. Roger then contacts Doof through the intercom, berating him for having Melanie to work for him, but Doof taunts him back by saying that he's the boss of him. After being given a stack of legislation papers to sign, Doof notices another time rift sucking up his snowglobe and orders Melanie to bring in another one, only to find out in horror that Melanie doesn't even know what a snowglobe is. Doof then realizes that even with Do-Over-inator gone, the time rifts are still erasing a lot of things from existence.
Back in the void, Phineas and Ferb collect all of the things that dropped into it. Suddenly, they see the tigers and then snowglobes falling from the sky. They run away from the impending danger.
Candace is still trying to convince the gang that she had two brothers and that they are friends. Baljeet then notices some fluctuations in the space-time continuum. Candace attempts to use this to convince the others, but they are still not interested.
Meanwhile, outside the Tri-Governor's Mansion, Monogram informs a moping Perry that Doof's anti-thwarting legislation is legitimate, and as a result, he is temporarily suspended from work until Doof's term is up. Vanessa sees Perry moping over his defeat and reveals her true reason why she's moving: she was accepted into O.W.C.A.'s internship program, but that she can't join it if she's living with her father (who happens to be one of O.W.C.A.'s wanted enemies). Vanessa then decides to tell him and convince him to let her do things her way, and Perry wishes her luck.
Back in Isabella's backyard, Baljeet is giving further explanations of the rifts in the space-time continuum. Only Candace is intrigued, but Isabella and Buford are bored out of their minds.
Meanwhile, Phineas and Ferb decide to distract the tigers by giving them a giant ball of yarn made of all the suspenders and Capri pants.
After finishing up his schedule as Tri-Governor, Doof returns to his daughter, who finally tells him about the internship. Doof is completely speechless by this, but Vanessa states that the only reason he builds his inators is simply to prove that he is evil, but that he only acts evil only as an obligation to his miserable childhood, not from what's coming from his heart. She also adds that the internship is something she really wants to do, and that she feels unhappy living in the Tri-Govenor's Mansion. Doofenshmirtz then realizes that despite his newfound success as the Tri-Governor, he too is unhappy in ruling the Tri-State Area. Vanessa suggests to her father to turn over a new leaf and become a good guy.
Before Doof could react to this, the loop starts over again, and Doof and Candace find themselves back in their beds, much to their anger. However, finally aware of Vanessa's true intentions, Doofenshmirtz tells Vanessa that he knows all about the internship and that he is turning over a new leaf for her sake. Vanessa is a little freaked out by this, but satisfied. Doof tells his daughter he plans to build one more inator, the Time-Straighten-Out-inator, which will help straighten the space-time continuum.
Candace brings the very sleepy and grumpy Isabella and Buford to the equally sleepy Baljeet's house. Once again, Baljeet and Buford have no idea who Candace is, and still cannot stand each other. Candace gets the device Baljeet was measuring the space-time continuum with and gives it to him. Baljeet is horrified to see how unstable it is. Candace once again tells them the situation of her missing brothers. Baljeet suggests that they can find the location of the next rift and throw a rope and life preserver into it to rescue them.
Doof and his daughter begin to build the inator, and Vanessa learns the situation of the Do-Over-inator's effects. Right on Doof's cue, Perry comes in expecting a trap, but Doof tells him he turned over a new leaf and needs his help. Perry, not really believing his frenemy, reluctantly provides his assistance.
After a few last-minute calculations, Baljeet discovers the next tear in the fabric, and it sucks up a groundhog. Meanwhile, Phineas and Ferb do some calculations of their own to try to find their way out, but the groundhogs mess up their calculations. In Danville Park, Baljeet finds the location of another anomaly. Candace throws the life preserver into it and calls out to her brothers to grab it, but the rope pulls Candace and the gang into the void.
Doof, Vanessa and Perry finish building the inator, but another loop begins before they can activate it.
Candace, Buford, Baljeet, and Isabella fall into the void and are greeted by the strange triangle-headed boy and the quiet green-haired guy next to him. Isabella suddenly looks at the triangle-headed boy and all the memories of her secret crush come back to her. Baljeet has a similar experience with spoons as does Buford with oranges. Candace is so overjoyed to see her brothers again. Baljeet believes that the void they are in exists outside the flow of time and Candace reveals to him that the days were getting shorter. This worries Baljeet because as the time pocket disappears from existence, everything else in the void will also cease to exist, including the entire gang.
Doof once again meets his daughter and once again begins building the Time-Straighten-Out-inator. Perry comes in to help once again as well.
Baljeet demonstrates the cause and effect of the shrinking of the space-time continuum with a paper towel and a hook. He then begins to wonder how Candace was unaffected by this and how she knew. Candace just nervously looks at the others and tells them not to question it. Baljeet then tells them that something has to be built to stop the looping once and for all. Buford then sees the Do-Over-inator, but Candace inadvertently reveals what it is. She finally confesses to the gang she was the one who pushed the button because she was so eager to bust her brothers. Buford suggests pushing the self-destruct button to negate the effects, but Baljeet warns that if they push it in the void, they will be unable to go back to Danville and be forgotten forever. He suggests finding a way to get both themselves and the inator through one of the rifts back to Danville so that they can push the button and destroy the machine. As such, Phineas and the gang get to work building a catapult. The gang gets into the catapult and Baljeet makes a calculation of multiple rifts coming. The rifts appear and cars begin to fall out of the sky. After Baljeet gives the coordinates, and Phineas adjusts the catapult, they launch themselves toward the rift, which appears in the nick of time and sucks them in.
Doofenshmirtz, Vanessa and Perry finish the inator faster than before. Doof tells the others the 55% of chance will lead to success, but Vanessa wonders what the 45% entails. Her father explains that 45% might bring about wiping everything from existence.
The gang make their return to the backyard, but the inator lands on the far side of the fence. Candace and the others run up to the inator. Phineas asks for a confirmation from Baljeet that destroying the inator will put everything back to normal. Baljeet confirms this and says they need to do it quickly since the time loops are getting shorter.
Suddenly, the time loop begins at the point where Doof and the others finished the inator. Doof once again gives the percentages. He assures Vanessa it is only a worst-case scenario. Vanessa then wonders what happens if they don't push, to which her father explains that if that happens the time pocket will be destroyed, but rambles too long.
Meanwhile, Phineas and the gang's time loop begins at the point where they returned to the backyard. They once again attempt to run up to the inator, but their time loop isn't quick enough.
Once again, Doof recaps all three of the percentages. He then asks Perry if he has any concerns, but before he can make the digga-digga-digga sound, the time loop ends again.
Phineas and the gang land in the backyard again. Candace then sees a spoon tucked into her skirt and gets an idea.
Doof shortens his spiel to saying that there is a lot of risk involved, but ensures the others this is their only option. Vanessa and Perry assure him they are with him.
Candace throws the spoon at the self-destruct button, and Doof pushes the button on the inator. Both Candace and Doof spin around in a blue vortex, thereby successfully ending the loops and bringing everything back to normal. This is confirmed when Linda comes out offering orange juice, which Lawrence squeezed with a spoon.
Meanwhile, Doof gets reassurance that everything is back to normal when Norm comes in with muffins. Doof then wonders what he'll do next, since he is not good at being a good guy. Vanessa then tells him that OWCA is looking for some new recruits. Perry then discovers the inator was not plugged in, wondering what could've stopped the loops.
In the backyard, Phineas, Candace and the gang are enjoying their orange juice and sharing their favorite memories of their summer. They continue to bond and reminisce. At one point, Phineas and Ferb fist bump each other. Even Candace gives Phineas a noogie and laughs along with the gang. Meanwhile, Perry, Doof, Vanessa and Norm do some reminiscing of their own while enjoying some muffins.
After a camera pan up to the summer sun, the backyard becomes a concert stage where all of the main characters, with some backup from the Fireside Girls, sing and dance about their awesome summer and bid all their fans and viewers, "Thank you for comin' along!"
- Serious Fun
- To Do Today Rap
- No One I'd Rather Go Nowhere With
- When Tomorrow is This Morning Again
- Quirky Worky Song
- Do You Know the Muffin Man
- Platypus Walk
- Gotta Get Back in Time
- Curtain Call/Time Spent Together