Teacher in Role

The method "teacher in role" was developed by Dorothy Heathcote and Gavin Bolton during the 80s, for drama pedagogical execises. However, it's an extremely potent tool for teaching with roleplaying too. 
To most younger kids, play acting and dressing up in costumes is both natural and fun. They enjoy the playful manner acting within a fiction. However, teenagers (and even some adults) are so busy distancing themselves from anything that might be considered 'childish' in any way, and this includes roleplay, as it reminds them of the make pretend games that little children play.
One way of putting them at ease is by letting the teacher set an example. The more at ease with roleplaying a character you seem, the better the kids feel about the situation. And they enjoy seeing their teacher out of his or her usual context. Don't worry about losing their respect: On the contrary, most pupils think you are cooler after having seen you with a wig on.

One thing I find particularly interesting about teacher in role is that it has the potential to short circuit the otherwise asymmetrical relationship of power between teacher and pupil. You can, for instance, play a very flaky character, and suddenly the pupils have to take resonsibility for the situation. This puts them in an interesting position, where they can practise making self reliant decisions in a safe environment.