History: Mr. Mxyztplk was a court jester in the palace of King Brpxz of the 5th Dimension. The king was not particularly bright or adept at magic, so Mxyztplk pretty much ran the country, and amused the populace with simple magic tricks. He soon grew bored of this, and began researching tomes of secret knowledge, which were forbidden to the people of the land. He found two magic words that could send him to Earth-2 or return him to his home dimension. On Earth he amused himself with playing magical pranks and soon attracted the attention of Superman I. Mxyztplk accidentally banished himself by speaking the word that returned him to his home, “Klptzyxm.” He found that he could not return to Earth-2 for the equivalent of 90 days.

(Superman I #51) - The King of Zriff asked Mxyztplk to marry his homely daughter, because all the good bachelors had already refused. Mxy told him her face would stop a clock, and when he announced a royal edict that he would marry, Mxy claimed that he was engaged to Lois Lane, who he'd met on Earth. The king demanded proof, and told Mxy to produce her. Mr. Mxyztplk went to Earth and proposed to Lois Lane, refusing to stop causing mischief until she consented. Lois agreed on the condition that he prove he was a better reporter, thus forcing Superman to help her win and help her career. Mxy scooped her getting an exclusive interview with millionaire recluse Seymour Salmon and getting the exclusive on an experimental rocket. Perry White was worried about losing his star reporter so he gave Lois and Mxy the assignment of getting Superman to answer three questions. Lois seemed a lock until Mxy assaulted  Metropolis with a giant hot sauce jar, and while Superman cleaned up the mess he responded to Mxyztplk's banter and answered three questions. Lois told Superman she'd never forgive him, and the marriage ceremony started. When the preacher asked if there were any objections Superman claimed Mxyztplk was an imposter named Klptzyxm, and Mxy was irritated enough to speak his name backwards in defense of himself, sending him back to Zriff.

Through the years Mxyztplk kept returning to Earth-2, because he enjoyed matching wits with Superman I and tormenting him. Due to the Crisis on Infinite Earths, Mr. Mxyztplk's existance was erased from DC continuity.