In the episode (I forget the name) where Mr. Burns goes broke and Lisa helps him get back the money from recycling...

Here's the slipup:

Mr. Burns stays over with Waylon Smithers, and offers to help clear away some crockery. He uses a pair of tongs to first take a plate (I think) to the sink, and then picked up a cup and saucer, which he drops on the floor. A smash is then distinctly heard. When the camera angle changes, there are no smashed up bits on the floor.