You would not believe how many times I've heard people refer to Whiskey as "she". My father-in-law in particular continually asks how "she" is doing - sometimes, when he's on the phone with us, I hear my mother-in-law in the background yelling "HE! HE! HE'S A BOY!"
When someone asks me about my cat and says something like "How is she doing?" I usually say something like, "Oh, Whiskey? He's doing fine, a real bundle of energy." I indicate the correct sex without making a huge point of it. But it seems like some people believe all cats are female ... in which case, uhhh ... where do kittens come from?