We had a feline mistaken sexual identity episode, too. My cat Misty Blue got out ONE day and in that ONE day got herself knocked up. To teach me a lesson, she had 6 kittens. We kept them all 'til they were a year old and had them spayed/neutered and started to adopt them out.
One of them had a little moustache and was quite wild. We named him Watson. We thought he was a male 'cause as he was running away, we could see two little round things under his tail. Well, when Watson was about a year old, all of a sudden he started rubbing up on us and flipping over to be petted and being all friendly.
My husband and I would ask each other, "What's up with Watson all of a sudden?" Then, one day, Johann said, "you don't think Watson is a female and she's in heat, do you?" My jaw dropped and I picked him up. Sure enough, those two circles were just round black marks against her white fur and she was indeed a female and was indeed in heat. So, her name is now "Miss Watson" and she was spayed immediately after she got out of heat.