Many times he arrive in lesser planes everything suddenly messes up looking cartoonish with e.g buildings having mouth,eyes becoming sentient and all that then he transmutes or poof things elsewhere or out of existence, basically reality in general messes up cause of him.
E.g on his profile
Reality Warping (Mister Mxyzptlk's main ability is Reality Warping. He is able to perform a large variety of feats due to this ability. Turned all the signs in the city upside down.[5] Turned Clark's reflection upside down and made his tie act like a snake.[6])
Reality Warping and Magic (Mister Mxyzptlk's main power is reality warping, and his primary source of power is magic - Fifth Dimensional Magic, to be more specific.[22][23] He can warp reality and whenever he leaves, the effects of it vanishes.[24] Erased Metropolis from the map, but once he left, it was back to normal.[25] Warped reality so people won't be able to say names backwards.[26] Granted everyone's wishes.[27] Altered the reality of the entire planet to make everyone's gender the opposite of what they should be, except for Superman's.[28] Warped reality on a planetary scale. Destroyed and recreated every reality in the multiverse.[11]
Reality Warping (Mister Mxyzptlk's main power is to warp reality.[70] He can[71] do[72] almost[73] anything[74] with this[75] ability.[76] His reality warping is said to defy transcend the laws of physics.[77] Unlike his previous incarnations, this version's reality warping[78] does not come from Fifth Dimensional magic.[79] Emperor Joker manipulated the reality in numerous ways with Mister Mxyzptlk's powers. He was able to reshape the world and reality, as well as the minds of everyone. In this new reality, the Justice League has been replaced with villains such as Bizzaro. Jimmy Wilson has been changed into Bizzaro's sidekick, turned Linda into a mindless priestess, and Lois Lane into a tyrannical business tycoon. And even Mister Mxyzptlk was changed by the joker. He was even able to warp heaven and hell into his mad image. Jokerized the Spectre.[80] Was going to unimagine reality out of existence.[81][82][83][84])