OK there was a movie about this boy and I don't remember much... but this one part was about some girl he knew having a birthday party. She didn't want to invite him but she had to or something. Anyway he lands up doing something mean. The song was that one... "its my party and i'll cry if i want to..." I think he threw her presents into the pool or something... you know... he might have been afraid of clowns because I think there was something about a clown night light that started a fire or blew up or something... and he may have been a foster kid... I don't remember maybe I'm confusing 2 movies? Please help!

Hi,
I believe this is the movie you are looking for, Problem Child 2, though it has been a while since I have seen either this movie or its predecessor:

http://www.imdb.com/title/tt0102719/

It does fit the description though. I hope this is it. :)

It's actually Problem Child 1. Both movies are still pretty good.