This is a bit similar to the corrupt your wish game. Someone posts a phrase and the next person comes up with a plot twist for the previous post.
So it'd go like this:
1. Sally has a cute little hamster.
2. PLOT TWIST! The hamster can talk in a deep manly voice.
3. PLOT TWIST! Sally is the hamster!
etc.
The more ridiculous and silly the twist, the better.
So I shall start:
Jack walks to the park.