Miketrap

Summary
-Mike Afton is Springtrap. William Afton was springlocked too, but in an another suit.

Proof
Scraptrap looks too different from Springtrap

Springtrap comes on screen after Michael declares that They (presumably the children) thought that "I was you" ('you') being William Afton. Also sounds Mikes voice robotised after the words "I will find you"

Counterproof
Mike was confirmed to be killed and rendered reanimated corpse by Ennard, but in the Night 5 cutscene the man in question is gushing blood, which a corpse would not do if it had already been one in the first place.