This is such a great method--it keeps your cats clean, for one thing. Plus, it's the worst thing you can do to them, so it works great to both punish the cat and relieve your own personal tensions.

The rules are simple:
1. Put a little shampoo in the toilet.
2. Put the cat in the toilet and shut the lid. The cat will suds itself up nicely, but you may have to sit on the lid. I do.
3. Flush the toilet until the cat is soap-free.

Your cats won't like you for this, but they'll forgive you eventually. And they come out sparkling clean.