Never been to a party that was 100% crap, I think that's 'cause I'm quite choosy about which ones I go to. I have, however, had a notably crap experience in the run-up to a party:
Back when I was in uni, a girl on our course decided to host a 'Tim Burton party' where everyone had to come dressed as a character from one of his films. I felt this was moderately pretensious as a party idea, but to be honest I quite fancied the girl at the time, and I knew from past occasions that her and her flatmate and their immediate circle of friends were all good fun, so I reckoned if the party had a lot of poseur types I could just hang out wiht people I knew.
However, I'm not exactly the best at dressing up, so after faffing about with various ideas, I decided that my best bet was to go as the Joker, as performed by Jack Nicholson. I was making a decent stab at it, but thought I really needed a proper approximation of the jacket and tie for it to work. There was a charity shop near my flat where I knew I could pick up clothes for very little money. I went in there on the afternoon of the party, found a tie which I still think is pretty nice, and a sure enough, a purple jacket - only problem is that is was obviously designed for a female wearer.
I marched up to the counter with, and got just a bit of a look from the male assistant. Now, what I should have done was just ignored him, shoved over my money and got out of there with the clothes pronto. But instead, I blurted out "Uhhh.. the jacket's not for me." He was like, "Oh right?", and then I had to go and say "It's, uhhh... for my girlfriend, it's her birthday soon. She likes purple stuff, and she's keen on giving to charity, so I thought I was quids in with this." He obviously didn't believe a word of this and started to joking to his female colleague about how I would probably be putting it on as soon as I was out on the street. I left with a very red face.
So the actual party was still a laugh, but as you've probably guessed, this was mainly an excuse to tell that story. Needless to say, I've never been back to that shop.