Oh, I LIKE the idea of returning villans! In fact I had thought of that, but decided not to bring it up (kinda off topic)

I can just imagine Jack and one of the villans coming head to head in a "disagreement" over the Hulk, as in "Bring Me the Head of the Hulk" and "Prometheus".

Mike Cassidy and LaFronde were incarcerated, one would imagine, by the end of the episode, but there are plenty of villans who just "got away", ready for a reappearance at some point.