Before I begin, I'd like to state that the following is NOT written by me. I found it on the Spongebob wiki! This is just a simple plot summary! And btw, this is my FAVORITE movie ever <3
The film begins with a live action credit sequence, in which a group of pirates retrieve tickets to The SpongeBob SquarePants Movie. The pirates then sing the SpongeBob SquarePants Theme Song. The pirates enter a movie theater and raid it, and sit down to watch the movie.
The movie properly begins with an emergency situation at the Krusty Krab, complete with police helicopters and news reporters. Eugene H. Krabs, SpongeBob's boss, explains to the reporters that a customer ordered a Krabby Patty with cheese, but found no cheese. Suddenly, SpongeBob SquarePants, "the manager", arrives in a sleek sports car. He enters the Krusty Krab, he takes a piece of cheese from a suitcase full of high-tech equipment, and slowly puts the cheese in the Krabby Patty. The day is saved, the crowd starts cheering for SpongeBob. Their cheering soon degenerates to the sound of SpongeBob's alarm clock, and he wakes up, revealing the opening scene to be a dream.
SpongeBob is extremely excited, as today is the grand opening of "The Krusty Krab 2" and he boasts to his snail Gary that he'll be the manager since he was Employee of the Month 374 times in a row. After preparing himself for his day, and greeting his neighbors Squidward Tentacles and Patrick Star, SpongeBob goes off to the Krusty Krab. Then we see a news flash about the Krusty Krab 2. Plankton is watching it all from a telescope. He is jealous. He is this way because he never had a customer. He envies Mr. Krabs, and states tried every plan in his cabinet from "A to Y". There are actually 26 letters of the alphabet, and Plankton doesn't notice it at first, but Karen tells him. Plankton finds "Plan Z" in the back of the drawer. He smells it. It's lemon-scented. He goes outside, only to be stepped on by SpongeBob. He pulls Plankton off his shoe, then runs off again. Meanwhile, Mr. Krabs is preparing the grand opening ceremony of the Krusty Krab 2, which is an exact replica of the original and is located directly next-door to it, the only difference being a giant glowing "2" sign. SpongeBob rushes up to the stage to accept his promotion, but Mr. Krabs announces that Squidward is the new manager instead, much to SpongeBob's shock. Mr. Krabs tells a heartbroken SpongeBob that he is too immature and childlike to handle the task, and SpongeBob sulks away, saying "I'm ready...depression." Patrick suddenly flies by, naked, with a spongebob pennant in his butt, and crashes into the set, causing a fire.
Meanwhile, Plankton flies towards King Neptune's castle, as part of "Plan Z". Inside, Neptune is attempting to punish his royal crown polisher for touching his crown, but is stopped by his intelligent daughter, Mindy. The brutish and tyrannical king tries to explain to his daughter that he must enforce his power as king in order to be respected, and that she will have to do the same when she is Queen. He begins to explain the importance of his crown, and as he talks, Plankton arrives and steals it. Neptune, who is bald, is horrified to discover that his crown is missing, Plankton having stolen it.
Meanwhile, SpongeBob is at Goofy Goober's brooding over his loss. He tells himself to get it together, and does, until Patrick arrives and mentions the new manager, and SpongeBob starts crying again. He tells Patrick that Mr. Krabs called him a kid and didn't give SpongeBob the job. SpongeBob starts to leave but then Patrick gets a Triple Gooberberry Sunrise, and SpongeBob comes back. They begin to eat dozens of bowls of ice cream. The two become "drunk" from all the ice cream, and SpongeBob falls asleep in the restaurant, experiencing hangover-like symptoms the morning afterwards.
Meanwhile, Neptune arrives at the Krusty Krab after receiving evidence planted by Plankton of Mr. Krabs stealing his crown, with the intention of executing Mr. Krabs. Krabs denies stealing the crown, but a message then plays on the phone of a man thanking Mr. Krabs for giving him the crown and saying that he sold it to Shell City. This call is actually from Plankton. Neptune asks if anyone has anything to say to defend Mr. Krabs, and a "drunken" SpongeBob arrives and insults Mr. Krabs out of spite, but upon realizing the severity of the situation returns to his normal self and stops Neptune from killing him. Mindy convinces her father to give SpongeBob a chance to prove Krab's innocence, and he and Patrick agree to travel to the dreaded Shell City, and return with the crown. Before departing, Mr. Krabs is frozen solid and Mindy, who Patrick develops a crush on, gives the duo a magical bag of winds to return home with.
With six days to retrieve the crown (there were originally ten until King Neptune and Patrick argued it down to six), SpongeBob and Patrick take the "Patty Wagon", a car shaped like a Krabby Patty. They soon reach a gas station located on the county line, where the hillbilly owners laugh at them, finding the duo and their vehicle stupid. They tell SpongeBob and Patrick that they wouldn't last for 10 seconds over the county line. When SpongeBob and Patrick cross the line, their car is immediately stolen by a thug. SpongeBob and Patrick then realize that they lasted for 12 seconds, and begin laughing at the hillbillies, who are dumbfounded by their idiocy, as they continue on foot. Later, they find their car parked at the "Thug Tug", a bar for tough, muscular fish. SpongeBob has Patrick distract the thugs so he can get the key. He is unsuccessful, and gets his hands dirty in the process. SpongeBob heads for the bathroom to wash his hands, and when he uses the soap dispenser, it produces bubbles. SpongeBob and Patrick begin having a "Bubble Party", but one bubble floats over to the leader of the "Thug Tug", who reminds the other bar patrons of the policy that all "Bubble Blowing Babies" will be severely beaten. The leader goes on a "Bubble Blowing Baby Hunt" by turning on the Goofy Goober Theme song, where the first person to start singing is determined to be the culprit. SpongeBob and Patrick struggle not to start singing, then the owner starts singing it to SpongeBob and Patrick, causing SpongeBob's eyes to water and Patrick to start melting, and they are only saved when Siamese Twins burst out in song. The other thugs begin beating them, allowing SpongeBob and Patrick to steal the key amidst the confusion and depart.
By the following day, Plankton, with Mr. Krabs incapacitated, has been able to obtain the Krabby Patty secret formula and begins serving Krabby Patties at the Chum Bucket.He stole the formula by sneaking by Mr. Krabs while he was frozen, went into his office, enter the safe code and stole the formula. Mr. Krabs was upset but you can not tell because he was frozen in a pose. But if this was a episode, he wouldn't get the formula with Mr.Krabs unfrozen, because Mr. Krabs would step on Plankton. Plankton starts sealing Krabby Patties at the Chum Bucket, along with free bucket helmet. He has also learned about SpongeBob and Patrick are trying to get the crown back and hired a professional hitman named Dennis to ensure that SpongeBob and Patrick do not reach Shell City. The next day, Squidward sees that everyone is wearing helmet buckets and after a woman tells him that Plankton is giving them free with the Krabby patties, he goes to confront Plankton, telling him that he was the one who stole King Neptune's the crown to get the Krabby Patties formula and decides to report him to King Neptune but before he leaves the chum bucket, Plankton activates a mind-control device, revealing that the bucket helmets are mind controlling helmets. Squidward tries to escape but the slaved citizens corner and capture him, taking down the last oppositor of Plankton in Bikini Bottom and transforms the city into "Planktopolis". SpongeBob and Patrick are traveling through a field of skulls, laughing over their victory at the Thug Tug. They see an Ice Cream Stand, but when SpongeBob goes to order, the old lady running the stand is revealed to be the tongue of a monstrous Frogfish using the Ice Cream Stand as bait. SpongeBob and Patrick are chased by a large sea monster, eventually driving off a cliff and getting out of the car just in time. The Frogfish is lured off the edge, and subsequently is eaten by an even larger beast that appears from the trench. Unable to pass through a monster-filled trench, SpongeBob decides to give up and accepts the fact that he and Patrick are just children. However, Mindy arrives and shows them what has happened to Bikini Bottom while they were gone, and gives them fake mustaches in the form of seaweed, convincing them that they are now men. SpongeBob and Patrick pass through the trench without fear (singing "Now That We're Men"), but meet up with Dennis on the other side. He rips off their fake mustaches and explains to them that they are not really men, and prepares to kill them by crushing them under his boot. However, before he can do so, Dennis himself is crushed by a gigantic boot, belonging to a monsterous scuba diver named "The Cyclops", who abducts SpongeBob and Patrick to the surface.
SpongeBob and Patrick wake up in a goldfish bowl filled with freshwater and sedimentary pebbles. They see the Cyclops making "knick-knacks" from dead sea creatures, much to their horror, and are soon taken out of the bowl and put on a table under a heat lamp, and start to dry up. Soon, SpongeBob laments that they have failed, and that Bikini Bottom will remain under Plankton's mind control, Mr. Krabs will be executed, and they too will die. Patrick points out a sign reading "Shell City: Marine Gifts and Sundries". SpongeBob realizes that they are in Shell City, which is in fact a gift shop. They see the crown, which is on display for nine dollars. SpongeBob then realizes that they did at least make it to Shell City, and did pretty well for "a couple of goofballs." They both shed a tear and begin singing the Goofy Goober song, just as they shrivel up. Back in the movie theater, the pirates mourn the loss of SpongeBob and Patrick, when a parrot advises them to keep watching the film. The "Tear of the Goofy Goober" slides down a wire into the power outlet, causing it to short circuit and let out smoke, which rises up and activates the sprinkler system, causing all the sea creatures to reanimate. As they beat up the monster, SpongeBob and Patrick grab the crown and carry it out to the beach. There, SpongeBob reads the manual of the Bag of Winds, and Patrick accidentally releases it, leaving them stranded on the beach. However, David Hasselhoff arrives and carries them across the ocean on his back. On the way back home, the big boot belonging to the same diver that kidnapped them rises up from the water, and an angry Dennis emerges from below it, who again attempts to crush SpongeBob and Patrick with his boot, but is knocked into the ocean by a floating sailboat. As the duo arrive over Bikini Bottom, King Neptune is about to execute Mr. Krabs, but is being stalled by Mindy. Hasselhoff opens his pectoral muscles and shoots the duo down into Bikini Bottom, where they crash through the roof of the Krusty Krab, the crown deflecting the trident blast that nearly kills Mr. Krabs, and ends up burning Hasselhoff. During their victory celebration, Plankton dumps a King-sized Chum Bucket Helmet on Neptune, also putting him under his control. As Plankton's hypnotized minions surround the heroes, SpongeBob makes a speech about being who you are, before transforming in a wizard and breaking out into a bizarre rock version of the Goofy Goober theme song. (based on the Twister Sister's I Wanna Rock) using his guitar's laser beams to destroy all the brain-control buckets with.
Plankton is trampled before he can escape, and the cops put him in a little cage and take him away. Neptune reaches an understanding not only with Mr. Krabs but also with his daughter, and thanks SpongeBob and Patrick. Squidward suggests to SpongeBob that he has learned that he doesn't really need to be the manager of the Krusty Krab 2, but SpongeBob eagerly takes the position anyway. Images shown throughout the end credits shown the sole two differences between the job of manager and fry-cook is that there is a giant hat with the word manager imprinted on it and an extra cent in his paycheque. Nonetheless, SpongeBob takes on the role of manager of the Krusty Krab 2 with great pride, as the film signifies the conclusion of the franchises's story...
Back in the theater, the usher tells the pirates to leave the theater so she can clean up.