Jimmy Negatron is a villain from the 2002 video game, Jimmy Neutron vs. Jimmy Negatron. He is Jimmy's evil counterpart from another dimension, and is not to be confused with Evil Jimmy, one of Jimmy's clones from the show. Unlike Neutron, Negatron wears a button up white lab shirt, brown pants, and black gloves. He also has a goatee. Curiously, while masquerading as Jimmy within the game's storyline, Negatron makes no attempt to disguise himself, and yet the other characters (except Ms. Fowl) do not realize he is not the real Jimmy (out of stupidity).
Negatron was supposed to be a villain on the show and was supposed to be named "Nummie Jetron", but he was erased and replaced by Evil Jimmy.