The extreamly rare male calico or tortoiseshell cat has three sex chromosomes,two X and one Y.
That's new to me, thanks, very interesting! All I heard so far was that if there are male calicos, they are most likely hermaphrodites and can't have babies.

Edited because it just hit me that in Luna's litter, there were 4 tabby girls (including Luna) and one boy - black and orange!

Kirsten