He is introduced as one of the members of the V Team as Slade and Anti Cosmo call him up to help them in their mission and like the all other villains in the group joins them. But they are defeated as usual.
Slade Strikes Back
He returned again and helped Slade again with his plans but they failed, It had to do with the horror of Joker's returning and every member was afraid of him. So he decided with the others to stop Joker angry at him for his actions
The V Team Island Adventure
This time he was in a protagonistic role with the rest of his team. He played his part and he joined forces with robot rival Bender and other heroes against Uka Uka. with his scientific knowledge he contributed to his victory against him
The Great Time Travel Adventure
Like the rest of the team he returned, And once lend his hand against villains including his future self against Marceline's dad and Darkwarrior Duck who has grand plans to take over.
After the adventure, he helps in the cloning of Ed before Eddy is hauled away on false charges of robbery by Carmelita Fox. Who wonders what he and the rest of the team are doing during Totally Mobian Spies? Dr. Nefarious was helping the V Team take back Mobius during the later parts of the story as part of their deal with the B Team who were keeping their eyes on their leader.
Allies and enemies
Allies: Lawrence, the V Team, Slade, Anti Cosmo, Hades, the Cosmic Empire, Ethan Lectric, the B Team (often)
Enemies: Ratchet, Clank, Joker, Uka Uka, Marceline's dad, the Master, Jack of Blades, M.O.D.A.B (at times), Alt Doof, Taurus Bulba, No Heart, Eggman Nega