Jellyfishing at Jellyfish Fields Music Blowing bubbles Krabby Patty flipping at The Krusty Krab Dancing Hanging out at Goo Lagoon Sandboarding Karate training reading spending time with his friends Annoying Squidward just for fun with Patrick
He and his show have been referenced several times in the show.
When SpongeBob discovers Plankton had taken over the Bikini Bottom, a porthole opens and Goddard comes out right in front of him and Gary, scaring him. His screen opens and Jimmy Neutron appears on it and explains to SpongeBob that Plankton teamed up with the rest of the Nickelodeon villains, Vlad Plasmius, Professor Finbarr Calamitous and Denzel Crocker. SpongeBob then follows Goddard through the porthole to Jimmy's Lab.
SpongeBob arrives in Jimmy's Lab where he meets Jimmy, Danny Phantom and Timmy Turner. SpongeBob then teams up with the other Nicktoons on their mission to stop the villains and save their worlds.
After the villains were defeated and their worlds were saved, SpongeBob says Jimmy can visit him in the Bikini Bottom anytime and they become friends.
SpongeBob meets Timmy and his GodParents again a couple more times in the other Nickoons games. In Nicktoons: Battle for Volcano Island, SpongeBob, Timmy, Cosmo and Wanda and the other Nicktoons team up to stop an evil enemy called the Mawgu. Jimmy Neutron is the only Nicktoon that's not a playable character but instead the one who always makes contact with SpongeBob, Timmy, his GodParents and the other Nicktoons.
In Nicktoons: Attack of the Toybots, he, Patrick and Tak find Timmy and his Fairy GodParents in Calamitous' Toybot Factory and save them. He, Patrick and the rest of the Nicktoons then battle their way to fight of Calamitous' Toybot army.