A youthful and red-haired imp from the Fifth Dimension of Zrfff with magical abilities that easily affect Superboy. He can be forced back to his home dimension (most chronicles say for a period of one month to ninety days) if he says his name backwards ("Kltpzyxm").
Superboy first meets Mxyzptlk when the mischievous imp crosses over into our universe after running away from his parents. Meeting the Boy of Steel, Mxyzptlk decides to play pranks on him, making him a laughing stock. Superboy thwarts Mxyzptlkâ€™s attempts, which incenses the imp. In response, Mxyzptlk creates a Jor-El ghost to convince Superboy to leave Earth. However, Superboy realizes the ghost is fake because the color blind Mxyzptlk has reversed the red and green in Jor-Elâ€™s outfit. Fuzastl, Mxyzptlkâ€™s father, sends a message to Earth that tells Superboy how to send his son home by convincing the imp to say his name backwards. Tricking Mxyzptlk, Superboy sends him home to the Fifth Dimension. This defeat at Superboyâ€˜s hands is the beginning of a feud between the two that lasts for several years, when the two opponents are known as Superman and Mr. Mxyzptlk (SB No. 78/3, Jan 1960: "The Ghost of Jor-El!").
Superboy next encounters Master Mxyzptlk in a September 1960 chronicle when he and Krypto are battling the Kryptonite Kid and his Kryptonite Dog. While the duo threaten the lives of Superboy and Krypto with exposure to Kryptonite radiation, Mxyzptlk arrives at the last minute and rescues them with his 5th-Dimensional magic and sends the Kryptonite Kid and his dog to jail in the 5th-Dimension. When Superboy questions the imp afterward, Mxyzptlk replies:
"That would have spoiled everything! If you were dead, I wouldn't be able to make you miserable with zany tricks for many years to come! Nobody can deprive ME of the pleasure of tormenting you! I've saved you this time, but next time you see me. . . WATCH OUT!" (SB No. 83/1: "The Dreams of Doom").
Superboy also encounters Mxyzptlk on several later occasions (for example, Adv No. 306/1, Mar 1963: "The 5th Dimensional High School"; SB No. 120/3, Apr 1965: "The Invulnerable Imp!"; SB No. 131, Jul 1966: "Lex Luthor, Imp!").