I had one of these a month ago, I was supposed to be working at the pub, ended up being let off at around half ten, called a mate and met up for a drink, bumped into someone else as the pub was closing, went with them to Drum n Base, met up with other mates there and had the most amazing time ever.
A similar thing happened this weekend and it was very pleasant. It was The Fizz' birthday, the plan was to go to Turnmills in London, so we got on the bus around half nine (listened to 20 year olds sing karaoke all the way there, not only this but they were drinking and dressed as pirates, lol...was rather funny in an irritating/funny way). Arrived in Farringdon, went to the pub to meet people, pub closed one person had turned up, located another bar open till late finally others turned up, drank, partied, 2.30 bar shut, off to Turnmills more drinks, chatting for me, dancing for others. People left, people turned up and I ended up staying in London until Monday morning.
Fucking brilliant weekend and here's to more nights in a similar sense. I love random nights.