I remember reading a fic a while ago about Dean being transgender. I'm sure it was on fanfiction.net, and I'm almost positive the title was "Tomcat," but I can't find it anywhere. In the fic, I believe Dean came out as trans when he was an adolescent when some guy was telling him off for checking out his girl and called Dean a lesbian, and Dean got defensive saying he wasn't a girl. John was accepting and told Sam that Dean was his brother now. It ended up being Wincest when Dean and Sam grew up, and when they had sex, Sam asked Dean what he wanted Sam to call his junk and Dean jokingly said Sam should call it a "tomcat" instead of a pussy, but both Sam and Dean ended up getting a kick out of that term.

Now that I think about it, I might be combining two different trans!Dean fics. But please, help me find it.