Just a question for clarification: you're looking for an omnipotent, omniscient, eternal, personal entity who can bodily manifest and takes interest in human affairs? The belief in whom is documented in the ancient world? Is that what you're asking about?

I'm somewhat familiar with the character of Q; are you looking for an entity who loves toying with people and playing games with them?

Many of the Greek gods were like that to some degree; witness Zeus and Hera's respective transformations of Io, or Aphrodite, Athena, and Hera's bribing of Paris, or Dionysus's turning a ship into a floating vineyard and then the sailors (who had jumped overboard in fear) into dolphins (hey, it let them swim away!) I don't know of any who did it to anywhere near as large a degree as Q, though.

You might be interested in the American Southwest legends of Coyote, as well. From the very little I know of him, he's a consummate trickster who's much closer to Q than any European deity.