Lloyd in Space (2001)

Lloyd and his friends notice all the girls passing around notes and they wonder what the notes say. So Eddie gets hold of one the girls' notes, and it says ""You're Invited To A Girls Slumber Party! Don't Tell Any Of The Boys About The Party!"" So Lloyd sneaks into the girls' slumber party (while dressed up as a girl) and he tries to find out all the girls' secret without anyone finding out that he's really a boy.