This is my favorite type of transformation. But I'm not sure what to call it, and it kinda take two completely different forms.
Form 1: Losing an "internal" battle with your body
I love transformations where the character is trying to hold back a transformation that is being forced on them.
Examples:Wasp in the Avengers cartoon
https://www.youtube.com/watch?v=IPP81q_xId0
Sandra from Inhumanoids
https://www.youtube.com/watch?v=jDKyL6y7FZ8
Form 2: Losing the "external" battle. AKA joining the horde.
Scenes where there is a threat of mass transformation and a hero character is lost to the other side.
Examples:
Diana from Martin Mystery into Alien/Lizard
https://www.youtube.com/watch?v=cZUqShldMgE
Lizard Transformations in this Spiderman cartoon (unfortunately only female TF is off screen)
https://www.youtube.com/watch?v=JCE64ruoe2w
Are you guys into these? And if so, how about we share our favorites?