In the console version, French Narrator, Gary, Goddard, Jack & Maddie Fenton, Walker, The Box Ghost, Sam Manson, Tucker Foley, The Purpleback Gorilla, Squidward Tentacles (mentioned), Sandy Cheeks, Patrick Star, DoodleBob, The Flying Dutchman, Karen (Plankton's computer W.I.F.E.), Mr. Krabs, Jorgen Von Strangle, and Cindy Vortex appear.
In the GameBoy Advance version, Johnny 13's shadow, Vlad's animal ghosts (from episode Maternal Instincts), Nega-Timmy and Jimmy's nanochip pants appear.
In the DS version, Patrick Star and Chester McBadBat can be seen.
In console version, in Jellyfish Fields level, the player can see the statue of Kevin the Sea Cucumber (from episode I'm Your Biggest Fanatic).
In console version, this is the second time Crocker is in Fairy World in his battle suit. The first was in the first Jimmy Timmy Power Hour special.
In the GameBoy Advance version, Danny can be seen without his DP emblem.
In the GameBoy Advance version, during dialog, the player can see some images from episodes of all four shows: Danny Phantom's Bitter Reunions, SpongeBob SquarePants' F.U.N. & The SpongeBob SquarePants Movie, Fairly OddParents' Hex Games and Jimmy Neutron's Operation: Rescue Jet Fusion and Jimmy Neutron: Boy Genius.
This is not the first time Jimmy meets Timmy. They've met themselves and their friends in the Jimmy Timmy Power Hour trilogy.
SpongeBob usually wears his red helmet when he's doing karate with Sandy in the series, but in Nicktoons Unite! and its next two but not third ( which he does not have any karate gear at all ) sequels he doesn't.
In the GameBoy Advance version, in Timmy's Home level, when Timmy says, "Hey, why there are robots in my house?", the player can see Jimmy's room in the background.
In the GameBoy Advance version, in the intro Denzel Crocker is misspelled as Denzil Crocker.
In the console version, Wanda says that she and Cosmo have lost their powers. However, throughout the game she and Cosmo use magic as Timmy's main attack. In addition, she and Cosmo use magic to poof into the scene right before she says that she and Cosmo have lost their powers.
Jimmy Neutron refers to Cosmo and Wanda as Timmy's "Holograms", even though by the end of Jimmy Timmy Power Hour, he called them "Reality-bending Computer Programs".