With the big, flappy mouths, the huge googly eyes and the "not talking to you" position they take between rounds, it's like watching Muppets fight
While fairly cartoony, this scene from Batman vs Teenage Mutant Ninja Turtles is pretty disturbing as Joker transforms himself and other villains with the ooze. Highlights of course being Two-Face's horrific experience and some of the sound details; listen closely, and you can hear Joker's mouth rip open whilst he just laughs through it
I found it on https://ifunny.co/video/you-may-spank-it-once-pgNHZWAt7 while looking at google images. I assume it's from Trevor Henderson he's the guy who made siren head and happy cat also other creepy art creatures.
So, I read I Have No Mouth and I Must Scream a few days back, and . . . that's pretty much it. I think a particularly grim highlight is when they realize they have no can opener for their food, causing Benny to devour the other's face out of sheer panic. So depressingly ironic, but the aftermath is horrific. Though, the ending may be even worse. Poor Teddy . . .
You could search google for image, but if you don't know what this being is then definitely you're lucky not knowing. Premium plastic surgery, tho.