Whenever I've seen kids play, boys will always say "I'm Superman!", "I am Spider-man!", or "I'm Goku!". I've been seen kids say "I'm Messi!" when playing football. With girls, it's different. Some will do the "I am Wonder Woman!" part, but when there is a lack of more characters, they create new ones. That's why you have the Mary Sue trope. Some girls will say "I'll be Indy's sidekick", but other insane ones won't say "I'm Indy", but "I am Ludovika Fantastica McGuffenzco-Groberthenst, the super smart and capable doctor scholar archeologist philosopher who's gonna be better than Indy!" Kennedy's that type.