No part of you isn't going to love this video -- unless you are one of the people who's birthday party was crashed by these insane entertainers.
Then you're going to LIVE for this video!!!
It's Katy Perry at her finest as she crashes three kids' birthday parties, a bar mitzvah and a 90th birthday celebration as the craziest carton of characters ever assembled.
She's gone undercover -- and she OWNS it!
Ch-ch-check out the video for Birthday here (above)!
Best part? It's a tie between when she reveals her true identity to all those kids and the freak out ... and when she eats a mouse and terrorizes the children forever!!!