I don't see a 'genderswitch' tag or anything like that, so ...

I've read a couple of Smallville stories where something or other about Clark's DNA suddenly turned him into a female, and now I'm wondering if there's anything like that in Supernatural fanfic.

I don't mean fics where the boys were born as girls, or discover transsexual yearnings; I mean stuff where Sam and/or Dean were male one minute, then female the next without warning or permission, and have to deal with the change.  I figure there must be some witch or other form of supernatural power that could do that to them.

Don't care if it's Wincest, genfic, or even crackfic if you've got it.  Don't care if the sex scenes are homo or het.  I'm just curious if there's anything like that out there.

Thanks for any and all help.