I ran a one night goofball D&D campaign with a few friends that was mostly cheesy jokes and fighting pirates. We laughed a lot, even if the campaign wasn’t very good – I tried to give the illusion of depth, but it was pretty closely welded to the rails.
It started in a tavern – I make a point of all of my non-serious campaigns off with starting in a tavern – and the players were supposed to talk to the pirate captain, weeping into his mug of rum alone at a table in the corner.
But the players wanted to know if there was anyone ELSE in the tavern to talk to. So I improvised a little bit, and told them there was also a table of six hooded figures, off at a table in a shadowy corner, their faces hidden by their crimson robes. One of the characters insists on talking to them before they have a chat with the pirate captain, so he pulls up a chair, plunks down on it, and tries to start up a conversation.
“Hey, uh, dudes. What’re you up to tonight?” (We’re not big on role-playing on screw-off nights.)
“We were just talking about our problems finding a band of adventurers to solve our little… problems.”
“What’s the mission? Who are you guys?”
At this point, the speaker from the group pulls the hood down, revealing a slender face with long, pointed ears and sky blue eyes. He looks directly at the player character and says, with a hush:
“We’re representatives of the North Everonian Elf-Boy Love Association.”
The player character stood up, walked over to the pirate, and started right onto the rails.
That was the last time they let me DM an off-night game.