Action Comics # 243 (Source Superman.wikia.com)
5. Lion-Headed Superman
Yes, this is a comic book where Superman has been turned into a lion man. It’s probably the defining image of the silver age, and it goes a long way toward explaining why old-school Superman comics are so gosh-darn fun to read. Wackiness is GREAT FUN. So, a story in which a descendant of the mythological being Circe gives Superman mineral water that turns him into a lion man because he won’t marry her is kind of my favorite thing.
He flies around helping people while hiding his lion-face, even though this is the DC Universe and stuff like this happens every other day or so. Superman eventually heads back to the Fortress of Solitude and checks the library, finding a book that explains to him how to create an antidote for his lion-head. Because Superman has a vast and extensive library of books about curing Lion-heads, apparently.
