Rotor: Rotor woke Tahu up one night to inform him that he was taking over the House. Tahu sliced off Rotor's arm, then got Omega Turtle to eat him.
Von Nebula/Von Black Hole: This odd set was first introduced in the fridge, eating Levacius and TLhikan's breakfast.
Fire Lord: After Levacius found Von Nebula in the fridge, he called the exterminator, and Fire Lord showed up.
Evo: Evo arrived along with the rest of the Hero Factory 2.0 sets after Brenmac called the exterminator due to all the Hero Factory sets in the house. When Mesonak died, ending up in the Core, Evo created a machine to bring him, Mesonak, and the other sets that ended up there back.
Nex: Nex was one of the sets that ended up in the Core at the same time as Mesonak. Evo devised a machine that brought them all back though.