Personally, I have a hard time determining when our cats are asking for the catnip to come out and play. It's usually a look that's indistinguishable from their "feed me" look and let's face it, food always goes over well with them.
But then, catnip seldom gets a nose turned up to it either — in fact, it's popular enough in this house that we have a corner and a stack of toys devoted to the stuff. However, we had never quite considered that one sort of catnip might be preferred over another by our fluffballs. They always go for whatever we bring home from the pet store.
Mikey Fivebucks thinks a bit differently when it comes to his felines.