I don't recall watching Superboy, and yet, when I think of a live action Mxy the first thing I think of is Pollard. Though in my head he is "that guy from that Star Trek episode". If asked, I would've speculated that I was recalling Lois and Clark, but apparently that's just a futile attempt to forget Howie Mandel.
He played it good. And in his second appearance they had Richard Kiel (Jaws) play Mxy's bully from the 5th Dimension and he gets Superboy and Lana to help him trick the guy to say his name backwards to send him back.
His first appearance was in season 1 and that on DVD has a commentary for that episode. And John Haymes Newton says Pollard was hired because he could float on air by himself so they could save on special effects. LOL
Superboy was a great show. Like the Flash it had a lot of comic book villains and plots, retooled slightly for live action, Metallo, Kryptonite Kid, Bizarro, Yellow Peri and more.
And although it was sort of stretch on how they changed the actor - Sherman Howard was the best Lex Luthor IMO.