I have been re-watching the Super Friends on HBO MAX and forgot how many times the League members were transformed. This is just some of them:
Wonder Woman and Superman as spirits in "The Ghost" (Season 2, Guest Starring The Gentleman's Ghost)
Superman and the Wonder Twins as Vampires in "Attack of the Vampire" (Season 3 Featuring Dracula)
The Twins and Wonder Woman in "The Beasts Are Coming" (Season 3)
Old Man Superman in "The Terror From The Phantom Zone!" (Season 3)
There are many more but thought i'd show off these.