Klptzyxm

The imp known as Mr.Mxyztplk [later changed to Mxyzptlk] first appeared in our dimension in DC comics Superman #30 [1st series, 1944] in a story by Jerry Siegel with art by John Sikela. He tells Superman that there is no way he can be tricked into saying the magic word “Klptzyxm” that will return him to his own dimension. Carelessly saying the word, Mxyztplk vanishes.