Stallone registered as an alien in the MIB Headquarters.
Michael Sylvester Gardenzio Stallone (pronounced /stəˈloʊn/; born July 6, 1946), commonly known as Sylvester Stallone, and nicknamed Sly Stallone is an American actor, filmmaker, screenwriter, film director and occasional painter.
He was classed as a cameo/uncredited when he was shown on the TV monitors to Agent J by Agent K at the start of the movie Men in Black, where he is revealed to actually be an alien.