Wow - you have never heard of a crush party?! Sure you are in a frat?
Anyways, a crush party is where your "crush" is invited to come. Sometimes they know who it is, if they are your bf/gf of course, or you are dating - sometimes they have an idea, and if you are really brave - they are clueless you like them! If they like you back, they come and be your date for the night. And if they come on the notion of finding who likes them - well who knows what could happen!
In the past for Crush Parties, we have done a Tailgate Party/Midnight Yell, Paintball, This place called Tombstone TX, which is a mock old west town where we had a dj & all - that sort of stuff. Very similar to a date party.