DOOM PATROL (vol. 1) #93 (February, 1965). Cover by Bob Brown.
Don't worry, dear reader, our hero, Robotman, hasn't turned evil! That's really The Brain, leader of The Brotherhood of Evil, who has taken control of Robotman's body.
That's not the strangest thing about this issue (and believe you me, the Silver Age Doom Patrol stories were stranger than anything Grant Morrison could dream up twenty-five years later).
The oddest part is that Cliff (Robotman) Steele's brain is transplanted no less than three times in this story, passed from body to body as easily as you would change batteries in a flashlight!