Okay, I decided on a different question--was going to ask how many whiskers a cat has, but that was too easy, and so here we go:

A multi-part one on Catnip:

Not all cats are affected by catnip, what percentage are not?
At what age does a cat start seeking out catnip?--Before this age, it is actually actively avoided;
If your cat has had his 'fix' of catnip, how long before it will affect him again?

Good luck, and this isn't a siamese question for a change!