Superman encounters a clone of himself who decays into a flawed version dubbed Bizarro. The clone continuously argues, "You no am Superman. Me am Superman!" until he discovers the truth of his origins—a secret cloning operation in the mountains, led by none other than Lex Luthor. Lex hopes to create an army of Supermen at his disposal.

A powerful imp from the 5th dimension, named Mister Mxyzptlk, starts annoying Superman by appearing every 90 days to cause trouble and mischief. The comical villain gets equally aggravated because Superman repeatedly tricks him into saying, spelling or revealing his own name backwards, sending him back to the 5th dimension. Mister Mxyzptlk returns with a proposition for Superman—get him to say or spell his own name backwards twice in a row, and he promises to leave Superman alone forever.