Just trying to remember some of the more impressive costumes:
Grover as a police officer
All four Teletubbies
The kid from UP in full boy scout uniform, balloons and all
Edward Scissorhands (one of John's friends)
Guys in tuxedos with really fancy masks
LOTS of guys in drag or some kind of skin tight leather
So on to the actual party...
First of all you couldn't get in if you didn't have a costume on. Once you were allowed in the door, the place was decorated from top to bottom including the hallways. There were three bars, all of which were open bar. There was a runway to show off your costume/dance/have performances. There were professional dancers (I don't know if I should really call them dancers because they also did some acrobatics in swings hung from the ceiling). There was even a dancer who did a routine with fire. Like I said, over the top. I was in awe.