Plastic Man #8 (1967)

Title: "The Unforgettable Wot's-Iz-Name" Plastic Man is crushed when a row of bleachers collapses on top of him. Physically he emerges unharmed, but a blow to the head gives him amnesia. It also causes him to mimic the behavior of the people around him. When he meets up with Waisel the Weasel, the crook is able to convince him that the police are actually crooks. He then leads Plastic Man on a string of robberies. Another blow to the head eventually restores Plas's memory. He then apprehends the crooks and attempts to restore his law-abiding reputation.