Here's a nice 'trick' to play on a student, which also gets a good story from a class.
You choose a student and take him/her out of the room. You tell them that the class has a story that this student must guess by asking questions. The class can only say yes or no, so the questions must start with auxiliary verbs. Go back into the classroom and tell the class what you've told the student. The only thing is, there is no story. The questions will be asked round the class, and the response of each student depends entirely on the last letter of the question. If the last letter of the last word of the question ends in a consonant, the answer must be yes; if the last letter of the last word of the question ends with a vowel, the answer given must be no.
The poor student is now brought into the class, given a board pen and the whiteboard to make notes, and begins to ask the questions. This may seem a rather cruel trick to play on a student, and it's true that you should choose a student who doesn't mind being the centre of attention. The interesting thing is that you actually end up with a story. The last time I tried this we came up with an octopus that had a party because his girlfreind had left him, and a bus crashed into the party although no-one was driving it!
There you go, where else will you find a story like that without the aid of illegal substances to aid creativity!