When I first started playing UO (10+ years ago), my first in-game friends and I would sometimes meet up in a bar after a hunt just to chat and drink in-game booze. Later, my guild would have casual sparring matches, which I (as a tamer/mage) did not take particularly seriously. I would just polymorph into a chicken and run around hitting people. Speaking of polymorph, I also amused myself sometimes by going to a common newbie hunting ground and polymorphing into a daemon to scare the newbies.

When I played EQ, some of my guildmates and I would get our characters drunk and then try to navigate the wood elf tree village (which had many long, narrow bridges). This commonly resulted in deaths.

This also reminds me of in-game weddings, which was not uncommon back when I was playing UO for whatever reason. I never did anything like that.