In this crossover with ""The Adventures of Jimmy Neutron: Boy Genius"", Cosmo and Wanda accidentally zap Timmy into the Neutron residence in Retroville while Jimmy finds himself in the Turner's house in Dimmsdale with no clue as to what's going on. Can Timmy's Fairy Godparents fix this mess, or will the two boys be forever stranded in each other's worlds?

Timmy returns to Retroville, but this time he takes Cosmo and Wanda with him. He and Jimmy fight over who gets to take Cindy to the Friday the 13th dance. Jimmy then returns to Dimmsdale as he takes Carl, Cindy, Sheen, and Libby with him. Meanwhile in Fairy World, the Antifairies escape from their prison again.

Timmy wants to become friends with Jimmy Neutron. While they are friends, they battle each other's enemies, and they create a new villian that they don't like. So they abandon him, but that makes him super evil now, and he takes Cosmo and Wanda's wands and Jimmy's brains. Now it's up to Jimmy and Timmy to solve the problem they got into.