My Name is Spider-Man!

I now have to address Kai as Spider Man or he's refusing to do anything. Not kidding.

ME: "Kai, go brush your teeth."
KAI: "I'm not Kai, I'm Spider Man."
ME: "OK. Fine then, go brush your teeth."
KAI: "Spider Man."
ME: "Are you kidding?"
KAI: "Spider Man!"
ME: "Sigh...[breathe a few breaths, then]...Spider Man, please go brush your teeth."
KAI: "OK Mom"