How not to settle a class

Teacher: Right class, we need to get stuck into this quickly because I have to disappear off to Pacific Radiology at twelve. Student: Oh, what have you done mister? Teacher: Impregnated my wife. *About a quarter of the class descends into hysterics, shocked laughter, mumbled comments about "I thought he'd say he twisted his ankle or something" and occasional congratulations and thumbs-up signs* Teacher: As I was saying, we need to get straight to work on this... I knew the effect my carefully chosen words would create, but I just couldn't resist...