Mr. Mxyzptlk

From HallsWiki

Mr. Mxyzptlk is a 5th-dimensional imp in DC Comics, who usually spends his time on Earth pestering Superman. Mr. Mxyzptlk's abilities are virtually limitless, but he prefers to pull pranks rather than do any real harm. Every 90 days he shows up, and Superman must find a way to get him to go back home; traditionally, this is by tricking the imp into saying his own name backwards, but in some stories, another equally peculiar goal must be met.

Mr. Mxyzptlk was a semi-finalist in the Battle of the C-Listers.