Shishi is always angry at everyone for no reason. He has attacked his own kind and was sent to planet Jupiter. He also ate the Tallests' snacks. Even if he looks as stupid as Zim, he is actually intelligent. Invader Shishi's partner is Invader Kat, and their leader is InvaderPD. His robot's name is Tik. Shishi has a little crush on PD. He trains with PD so he can be close to her. He always loses in fights with Kat and PD. The real reason why he's mad is because Tik is annoying him with his stupid remarks.