Hahahaha! This happened when I had my massive house party 5 years ago. A group of colleagues ended up on a street parallel to mine, on the same number, which happened to have a house psrty as well. Apparently they didn't realise until 15 minutes in. XDAwesome reaction of the host, btw.
Seriously, eh! i guess that's what happens on a Saturday night . . . cling a random doorbell and you're likely to be let in! :P HAHAHA