Ok, I literally just saw the OK KO special "TKO" just an hour ago, and I already saw important clues which lead to the creation of this theory.
When I saw the Shadowy Figure talking to KO from the bushes, I, and probably the majority of you immediately realized that he is Professor Venomous, from the episode "We're Captured." The lanky figure, purple skin, and freckles (or stubble, whatever you interpret it as) were a dead giveaway. I didn't think much of it and kept watching the episode.
After KO's transformation to TKO, I noticed some more important clues. Some major aspects of his transformation include his new messy hair and sharp teeth, among other lesser changes. Who else has hung around Professor Venomous and possesses these traits? His minion, Fink!
I believe that Professor Venomous previously showed Fink this "anger method" before showing KO. Sure, the messy hair could easily be dismissed as being a part of who she is, but it's very unusual for a rat to have sharp teeth like that. I believe that before her transformation, her hair may have been different, and she probably had buck teeth like Potato has, seeing as that in real life both rats and rabbits have buck teeth. Not to mention her violent personality, similar to TKO's.
So, to recap, similarities between TKO and Fink are messy hair, sharp teeth, and violent personality, all of which KO acquired during his transformation, and Fink likely acquired in a similar transformation. The only reason we haven't seen Fink exhibit the abilities TKO did is because there was no serious need to do so in "We're Captured."
Got anything to add to this? Got any points against it? Feel free to leave some reviews and tell me what you think!