When I teach creative writing I always use this exercise. It helps teach students a very basic lesson about plot: That it is not what happens that matters, but how you portray it. It is a lot of fun to do with a larger group of people because when they read their work out loud afterwards they take the story in all sorts of different directions within the same parameters.
This exercise is all about conveying two plot points. The first plot point is that two bank robbers enter a bank. The second is that two bank robbers exit a bank. Now a lot of plot can happen between these two points but these two points must be included in your piece.
Even though this exercise seems very straight forward there are a lot of different pieces to work with here. There is the bank robbers who could be hardened men, or drug addicts, or delusional children or any number of other things.
Then there is the bank robbery itself. Just because the robbers enter and exit the bank doesn’t mean that they get away with the crime. They could be leaving in cuffs, or empty handed. Or perhaps they are successful, if they are, how did they manage to pull that off?
Some writers will turn this into a funny piece, others into a tragic one, or one filled with action and adventure, but the wonderful thing with these two plot points is that they could go any number of ways. The way your piece turns out is entirely up to you.