Justice League Unlimited (2004)

S1E3 Kid Stuff

Title: Child's Play Plot: Morgaine Le Fey casts a spell that reverts Superman, Batman, Wonder Woman, and Green Lantern to their childhood selves after Mordred utilizes his sorcery to banish all adults from the planet, leaving only kids behind. As the heroes navigate their newfound innocence, they must find a way to reclaim their powers and restore balance to a world now ruled by youthful chaos.