The Fly (1958 film)/Headscratchers


 * The protagonist and the fly switch heads, but retain their memories and (most of) their personalities. How?
 * You're really asking that?.
 * A joke about the 1950s movie goes: "If both the scientist and the fly have human brains, where did the fly's brain go? "
 * To be fair the scientist's mind was slowly deteriorating to that of a fly, which is one of the many reasons he was so desperate to turn back.