A mummers play was a kind of folk play with a long tradition in at least Britain. The scripts were passed down mostly orally, and the performers were generally not professional, but simply drawn from any local populace. Because the scripts were passed down generationally, the audience generally knew the script as well as the performers, and, indeed, roles could simply be awarded to audience members during the course of the performance.
A particular Christmas mummers play was passed down in Stockbridge, England for centuries, which the Fifth Doctor and Nyssa witnessed and even performed in on Boxing Day 1899. It was based on historical events involving St George slaying the dragon, and the Doctor was surprised to discovered that he was a character in the play. This led him to conclude that he and Nyssa were actually part of the historical events — but not before he was forced to play himself to an audience only too prepared to boo his interpretation of the part. (AUDIO: Castle of Fear)
