Spiderman and His Amazing Friends, episode "Swarm"; Firestar was turned into an insectoid.
He Man and the Masters of the Universe, "To Save Skeletor"; Sorceress was turned into a harpy-like monster by a 2nd-rate lovecraftian demon-god.
Spiderwoman, "Dracula's Revenge"; Spiderwoman was turned into Spidervampirewerewolfwoman by the monster's funky monster rays, sadly she just missed out on getting a dose of rays from Frankenstein's monster and becoming a hybrid of the unholy trinity.
Incredible Hulk, "Doomed"; Bruce Banner's cousin had a memorable first transformation into She Hulk.
https://www.youtube.com/watch?v=aTr3gClwArQ