Watch Superman: The Animated Series - Series 2 - Episode 8 Online Free

To prove he's cleverer, an imp named Mxyzptlk comes from another dimension to play mind games with Superman. To get Mxyzptlk to return home, Superman must make the imp say his own name backwards. But then the imp changes the rules. Superman must now make Mxyzptlk say his own name backwards twice. While eluding the imp (who has turned into a missile), Superman gets him to spell his name backward twice with skywriting, banishing Mxyzptlk forever.