Nicktoons Unite!, known as SpongeBob SquarePants and Friends: Unite! in Europe, is a 2005 video game featuring characters and levels from SpongeBob SquarePants, Danny Phantom, The Fairly OddParents, and The Adventures of Jimmy Neutron: Boy Genius. Before it came out, a video game called Nicktoons: Freeze Frame Frenzy was released. It spawned 3 sequels named Nicktoons: Battle for Volcano Island, Nicktoons: Attack of the Toybots, and SpongeBob SquarePants featuring Nicktoons: Globs of Doom.
One morning, when SpongeBob SquarePants goes out of his house, he sees that Plankton has taken over Bikini Bottom and used multiple tank-like vacuums to suck away all of the town's civilians. He sees Goddard coming out through a portal and receives a message from Jimmy Neutron. He follows Goddard through the portal to Jimmy's lab and meets Jimmy Neutron, Danny Phantom, and Timmy Turner. Jimmy tells his interdimensional guests about his new invention, The Universe Portal Machine. As he says, it allows people to travel to other worlds. But Prof. Calamitous has been spying on him, stole his idea and created his own Portal Machine. With it, he brought Plankton, Vlad Plasmius, and Denzel Crocker to his dimension. They formed a Syndicate and proceed to steal energy from all the worlds. Since our heroes don't know where Calamitous' lair is, they start with saving all of their worlds first.
They go to Amity Park first and find Vlad. Vlad reveals that he uses his ghost-portal to steal ghost energy from the Ghost Zone. Vlad has also captured Danny's parents. Then, he sends the heroes to the Ghost Zone Prison. The Nicktoons escape the prison while freeing all the ghost in it, and defeat Walker. They break out of the prison through a portal and end up in Fenton Works. They see many Amity Park civilians possessed by ghosts, but manage to push them out. The Nicktoons go to the Amity Park Graveyard, which is a shortcut to Plasmius' castle where casper high used to be. When they go in, Jimmy realizes that there are generators that help Vlad keep the portal open. They find the generators, and destroy them, shutting off the portal. When they find Vlad, the Nicktoons defeat him and save Jack and Maddie Fenton without them noticing the Nicktoons. They also find out that the Syndicate is building something.
Next, our heroes go to Bikini Bottom to fight Plankton. They meet Sandy, and follow her to The Krusty Krab. Sandy tells the Nicktoons that they should find some guards which should help them find Plankton and the Jellyfish Factory. Fortunately, they found the guards. Sandy then explains that Plankton uses the harvesters to capture various Jellyfish, and is extracting power from their sting in the factory. Plankton also captured Mr. Krabs. Sandy told the Nicktoons that they must go into the Jellyfish Factory and free all the Jellyfish. After Timmy asked if they have any secret agents (since he thought that it's like a spy movie), Sandy said that they have an agent in Jellyfish Fields, who reveals to be Patrick, but he's been captured by a Jellyfish harvester. After destroying all the harvesters, the Nicktoons go to the factory but during the journey, they find themselves on the Flying Dutchman's ship and the Flying Dutchman is going to make them his new crew for all eternity. Luckily, the Dutchman frees them after they bring back his old crew. When the Nicktoons arrived to the Chum Bucket, they free Patrick, then free all the Jellyfish by opening the emergency vents. Later, they went up to the top of the Chum Bucket, where they beat Plankton and rescue Mr. Krabs. The Nicktoons find out that the villains are extracting energy for a Doomsday Device.
In Dimmsdale, the Nicktoons see Crocker has made the fortress made of gold. They also find a rainbow of pure Fairy Magic from the Fairy World that is ending there, so they go in. After they re-activate the prisms, they get transported to Fairy World, where they meet Jorgen Von Strangle. Jorgen explains that Crocker is extracting the magic from the Big Wand to feed the Doomsday Machine. After freeing the fairies, they go to The Big Wand, where they defeat Crocker. Danny figured out that every time they beat their enemies, they're running away, which was a part of a plan.also they find out that they can't trap them with fairy magic because it's against da rules
Finally, the Nicktoons return to Retroville, where Jimmy finds Cindy in his lab and he also receives a message from Calamitous that they've almost finished the Doomsday Machine and the Nicktoons can't stop them. After SpongeBob notices that Goddard has fleas, Jimmy says that Goddard doesn't get the fleas. Then, he figured out how Calamitous could spy on him; he was using a flea-bot inside Goddard. So the Nicktoons shrink themselves down and go to Goddard's stomach. They beat a lot of mini flea-bots throughout Goddard, and Danny, Timmy and SpongeBob gain Goddard's trust. They go to Goddard's head and beat the giant flea-bot. Jimmy used the flea-bot's circuitry and locate Calamitous' secret lair, which is situated under an old warehouse. When they get to Calamitous' Doomsday lab, they find The Syndicate in a wheel-like machine which shields them. They beat the Syndicate but they see that the Doomsday Device is still counting down to destroy the universe and it can't be stopped. Luckily, SpongeBob unplugs the Doomsday Machine and saves the universe.
After putting Calamitous in jail and the trapping the villains, the Nicktoons said themselves goodbye, but before they went, Jimmy gave them the Neutronic Recallers in case of another event like this. SpongeBob said that Jimmy can visit him anytime he likes, but then he said he should get going, so he won't be charged by Mr. Krabs for wasting his time (even though SpongeBob and the others saved his life from Plankton, whose imprisonment is unknown), Danny gave Jimmy a copy of the Fenton Thermos (since the copy thermos had Vlad trapped inside, Danny used Jimmy's Matter Duplicator to make a copy), then Timmy thanked Jimmy for lending him his Hyper-Cube for holding Crocker until Timmy and his fairies get back to Dimmsdale. After this, Jimmy says a familiar line: "Cindy, get out of my lab!"
- Heroes: SpongeBob SquarePants, Timmy Turner (with Cosmo and Wanda), Danny Phantom, and Jimmy Neutron
- Villans: Professor Calamitous, Vlad Plasmius, Denzel Crocker, Plankton
- Other: Sandy Cheeks, Patrick Star, Mr. Krabs, Flying Dutchman, Jorgen Von Strangle, Box Ghost, Samatha Manson, Tucker Foley, Cindy Vortex, Goddard
- Miniboss: Walker,3 Jellyfish Harvestors, Fleabot
In console version player can play with three computers and no other human players, or with a friend or two with the remaining computer(s). One can switch abilities, which have multiple uses. There are also things only a certain character can do. For example, SpongeBob is needed to use Bubble Bombs to blow up a pillar, Danny is needed to use Ghostly Wail on some glass, Timmy is needed to use Freeze Glove to freeze some water, or Jimmy has to shoot down some things with his Neutron Flare.
Goddard can be found in all four worlds (and oddly enough, inside himself) so he can upgrade the players weapons and abilities.