"Bad kitty" warnings?

When our kitties decide to "become bad" and "get" us, we know that
they usually turn sideways and hunch up, or as my friend calls it,
becoming a "witch kitty".

Then they will likely run and paw at us, then dash off into the other
room, daring us to follow, at our peril.

Well, my big 19-pound orange fuzzball "RJ" also has a very unusual way
to indicate that he's about to "turn bad". Here's RJ's pictu

http://www.waas.us/images/cats/rj-4.jpg

He lies on his side, and very briskly scratches his jaw and chin with
his hind foot. That is a signal. And I have zero idea how this came
into being, but when he does this, I'm being warned to "watch out"
because I'm now in the same room as a knucklehead kitty. Ha ha.

This scratching his chin to show he's going to be mischevious is a
very strange trait. Do any of your cats do something similar? Do they
have a special way to indicate that they are about to misbehave?