1: One of the character feels stinging pain in his back. Closer inspection reveals a treasure map tattooed on his back.
2: Some fae are tricky pranksters. Characters overslept in the fae magic. They wake up 6d6 decades later.
3: When they wake up for an unknown reason they have swapped bodies. So now that perky little Elven archer lady has to live in his fellow barbarian's body until they find a way to get things back as they were.
4: An owl accompanies the party after the night. It doesn't seem to be bothered by daylight hours at all and will follow the party in distance. This owl is actually super intelligent. He might be their guardian, just making sure they don't mess up anything the owl is guarding or it might be a spy.
5: All the magic-users spells are switched in his spell book. Randomly determine the new spells he has now. If there is no magic-user in party, all items of a random character are switched to something else. Dagger to spoon, backpack to foundation cream, rope to warhammer...
6: All characters recall horrible nightmares. Their hair's turned white.
7: Little zombie baby has crawled to sleep with them. They woke up in its horrible demanding scream. Instead of BRAAAAIIINS the zombie baby yells MOOOMMMAAAAA.
8: The rainstorm is horrible and everything is flooding. Now they aren't resting on solid ground but in a fast-flowing and dangerous river. Loosing equipment and staying unharmed is hard.
9: Panty-bandits raid the party. Instead of being interested in valuables they are after the panties. They are extremely nifty in stealing panties without alerting the victim. But someone might wake up his pants down...
10: Earth trembles but it is not an earthquake. It's actually the pack of vegetarian dinosaurs running for their lives not to be eaten by [T-Rex, pack of velociraptors, or similar carnivorous predator]. And characters' camp is on their path. Grab what you can and take cover or be mushed.
11: Characters are dreaming of an unicorn. What a nice dream. Except it ends as goblins slaughter it and bathe in its blood, cook its meat and make a relic of its horn. When characters wake up they hear a magical horsey shreak in distance.
12: Horrible insects have laid their eggs on characters' skins. Itching, papules, rash, fever ensured. Most horrible thing is when the eggs hatch and under your skin hundreds of maggots crawl eating their way out.
13: A shooting star so bright that characters even if eyes closed are blinded. Those who sleep for 1d4 days. Those who are eyes open (guarding the camp for example) 3d6 days.
14: What ever was surrounding the characters (woods, rocks, barn) has moved 1000ft. away when they slept. It's actually intelligent lifeform(s) what didn't like characters in/near it.
15: Where they sleep it's an old cemetery buried in soil, moss, undergrowth, built over... Try to sleep in ghost activity!
16: When they wake up there's duplicates of the party. Same equipment, same face, same personality. Who's who when both know they are originals!
17: One of the party members has died in unknown reasons. Now he's a ghost following his living fellow members. Does he enjoy his new ghastly benefices or are they trying to find out a way to get him back into the books of the living?
18: Drank or not all feel hungover. 3 penalty for rolls for next 1d8 hours. The reason is unknown, maybe they just didn't sleep well.
19: The moss grows really fast. So fast it has covered the characters and their equipment. It is extremely painful to take the moss off by ripping it* so there has to be another solution. But it might get some reactions walking around as a mossy figure.
*As much moss must be ripped off as character has CON. 2d8 damage per equivalent of one CON point moss ripped away.
20: What a pleasant night. You had dreams of all the adventures in the past and adventures to become. Gain enough experience points for your next level!
Original post by +Venger Satanis at http://vengersatanis.blogspot.fi/2013/04/things-happen-while-they-sleep.html
He wrote this in his blog so I contributed:
Tobie Abad was inspired to create his own "why they sleep" table. Check his out because he came up with some awesome stuff! If we had a couple more gamers in on this, we could forge a collaborative d100 "why they sleep" random table. Who's in?