McGrath barely beat me to it. A few years ago it was "quite the thing" to teach your cats to "toity in the toity." You could get a kit consisting of a small transparent plastic "cup" that sat on the porcelain under the seat. Sprinkle a little litter in it, and show it to the cat. As they get accustomed to it, gradually reduce the amount of litter, and when it's all gone, take the plastic out.

You might find the "training kit" at some pet shops even now. Some people just used Saran wrap for a homemade version. (Just be sure to remove the Saran if you have guests - it's a nasty party prank.)

But they never taught one to pull the little handle to flush after.

John