Theo Nott hadn't planned to go to Goyle's costume party. It wasn't that he didn't like Greg, though he didn't.  Greg Goyle was loud, vulgar, stupid, and rapidly drinking himself into the death he'd avoided in the war.  That, however, wasn't why he didn't usually go. It was just that he didn't like parties much, especially Greg's.  They were inevitably loud and as vulgar as the host, and he'd sip from one drink over an hour while no one talked to him then go home, more depressed than he had been before he'd arrived.  He didn't do well in groups.  He never knew what to say, or how to make small talk.  "So, you don't have a Mark on your arm," was too personal, though he'd had people say it to him more than once, hoping the answer would be that he did so they could ask to see it.  "Nice weather we're having," was both not personal enough and usually false.  "Did you read the newest article in The Journal of Potion Making on how cauldron material could be used to impact efficacy," was sure to make people drift away in boredom.