MISTER MXYZPTLK

Mister Mxyzptlk is a reality-warping imp from the Fifth Dimension and one of Superman's most persistent and eccentric adversaries. A mischievous trickster rather than a traditional villain, he uses nigh-omnipotent magic to pester the Man of Steel, governed only by self-imposed rules—most notably the requirement to return home if tricked into saying his name backwards.