Jimmy's worst enemies, the Yolkians from Jimmy Neutron: Boy Genius, come back and pretends to be nice, but Jimmy suspects something about the Yolkian's evil plan leading the town to turn against him and attend a Yolkian party.

Jimmy puts a `smart chip' into his trousers so that they will fold themselves, but they develop a mind of their own, and soon an army of trousers is on the loose.