The Randomness Ideas

*Someone important to the action is poisoned.  
*Your character is locked in a prison of some kind. The only way to get the key is by singing.  
*A coin toss takes on tremendous importance.  
*It was the last thing they ever expected to find in the kitchen 
*Your characters have to escape into a garden... Which, it turns out, is full of something other than flowers and plants.  
*Two characters fight over where they're each going to sit. It gets out of hand ... fast.
*Someone from the character's past shows up out of the blue, intent on revenge.
*Some part of your cast now has to rely on an unusual (for them, at least) method of travel. A reindeer, or hot air balloon, or roller skates... 
*Just when they couldn't slow down, your characters get caught in a local celebration, festival, or holiday.
*Just when your characters thought they could relax, the roof falls in. (Or a tree limb drops. Or the tent collapses. Or the mine caves in.)
*Whatever tool or skill or technology your characters were most relying on--it breaks. It stops working. It's faulty. Now what?
*Someone falls: through the flooring, through the ice, into quicksand, through the stairs. Wherever they are, the ground gives way.
*Time for a natural disaster. Storm, flood, fire, earthquake, avalanche... Send your characters scrambling.
*Two Characters are Secretly Related
*The Hero is Secretly the Villain
*A Fake-Ally is Secretly the Villain
*Multiple Personality Disorder
*It Was All Just a Dream or an Illusion
*Character was Actually Dead All Along
*Character Never Actually Died
*Fake or Virtual Reality World
*The Setting Is Not What It Seems
*The Timeline Is Not What It Seems
* 
All of these and more featured in the Random Roleplay .