Ohhh, that must REALLY have gotten Tuffy's goat. Cats hate to be mocked.
The fastest way to get Toby to stop doing something is to make fun of him for doing it. Sometimes I also use a disappointed tone, like "I thought YOU knew better than THAT, Mr. Toby!"
But that's so mean that I don't do it often. More likely, Becky and I will be stifling our laughter while assuring Toby solemnly that, yes, we DO understand that he INTENDED to fall off that chair, and that he was still dignified and awesome to us.