I met Vaughan Pratt at a math seminar a few years back, where he was talking about his current interest, Chu spaces. While we were waiting in line to get coffee, with the coffee stations labeled "regular" and "decaf", Pratt said, "But where's the context-free coffee?" and then laughed at his own joke. Later at lunch he was telling us about a physics experiment he set up in his pool shed; "My wife told me to do it in the pool shed so that if it explodes it won't destroy the house."