Mister Mxyzptlk (Earth-50)

"“It is I! The one and only Mister Mxyzptlk, straight from the Fifth Dimension!”"-Mister Mxyzptlk to Power Girl

Mister Mxyzptlk is an extremely powerful Imp from the Fifth Dimension. He's an enemy of Hulk and the Earth-50 Justice League.

Biography
Mxy first appears in the Fifth Dimension, sighing with boredom. He decides to ‘have some fun’, and travels to Earth-50. He witnesses the Alternate Future War from the sky.