A new amusement park is opened on the outskirts of Metropolis and Jimmy Olsen is assigned to cover it. The festivities are interrupted by strange occurances such as rides spinning backwards for no reason. Jimmy calls Clark Kent for help and Superman arrives moments later. Superman saves parts of the rides that have flown away even as a diminutive man nearby laughs in glee at the chaos.
The diminutive man stares at carousel and roller coaster nearby and Superman has to fly to the rescue. Superman spots the diminutive imp and flies towards him. The imp introduces himself as Mxyzptlk from the fifth dimension and says the only way he goes back to his home dimension for ninety days is if he says his name backwards and he's having too much fun.
Mxyzptlk encounters a man (secretly Clark Kent) who tries get him to read a piece of paper with his name backwards but the imp recognizes it as a ploy of Superman and refuses. Superman encounters the imp and challenges him to see if the hero can make him say his name backwards. Superman blindfolds the imp and carries fireworks into the sky with a request for the imp to read the first letter he sees. Superman removes the blindfold but the imp points out that the sky message is wrong and pronounces it the way it should be. With that, the imp fades away but vows to return in ninety days.
Clark encounters Jimmy and says he couldn't find anything wrong except a "mixed pickle".