Tony Bennett used to do a trick which I have seen done a few times since by others, but never as well as he did it. Maybe you have seen someone do it - somebody orders a coffee, Tony Bennett carefully brings it. Standing above the seated orderer, only to stumble slightly clumsily knock the cup over on the saucer, heading straight in the direction of the customer's lap. It's all a joke, the cup is empty. A little low tech, but done well it does make your heart miss a beat - and that's just watching, it must scare the coffee orderer half to death