Swamp Thing

Swamp Thing is a superhero who is a living vegetable. At a masquerade party in Gotham City, a wealthy party goer wore a very impressive Swamp Thing costume. But when Felix Faust drops in, he uses his magic to make it impossible for him and other guests to take of their costumes, giving them the powers of the monsters they resemble, thereby taking there identities.

Appearance
Technically he never appeared, but a man dressed up as him appears in Super Friends #28