Done the oxy-acetylene 'bomb' a few times ourselves, very funny. A simple trick one of the guys here did was when one of our salesman was selling a car to two young attractive girls. He thought he might have a chance with one of them, if not both. Anyway he left the showroom to get the car details and while he was out our prankster left a note on his desk in full view of the girls, but not visible from where he was sitting that read, 'Steve, Toby called for you, wants to say thanks for dinner last night and the flowers. Will see you at home tonight'. The girls never looked at him the same way again, despite his 'charming' ways.