A character from the old
DC Superman comics. While he's certainly an
antagonist it's hard to call him a
super villain. He was more mischievous than malicious, but the trouble he caused was real enough.
Most of what I know about this guy I learned from his appearances in the Superfriends Saturday morning cartoon where he appeared as a wiry old guy in an icky, mauve jumpsuit, usually levitating and spewing next-to-impossible riddles. He comes from the 5th dimension and is essentially omnipotent - now that I think of it, he sort of foreshadows Q. But that's another node entirely.
In the Super Friends series the only way to get rid of him was to say his name backward. That's a tall order as nobody could really say it forward (sounds like "mix-el-plik"). Superman did it once but I totally call bullshit - what he said was "slif-el-skim" - not remotely accurate, but the whiney twerp went mewling back to the 5th dimension anyway.
I hear that he also appears in the latest Superman cartoon incarnation (The New Batman/Superman Adventures) but I haven't been keeping track of that series. Perhaps someone who has can add a writeup...