I once threw this on my players, and they did this.
Kind of annoying, because it was a rather huge deal. It was a magical spell gone wrong (because of the players) because a princess wanted more power, but the country in question wouldn't allow a woman to get any more than she already had (IE she had less power than the king) so she tried to change her gender. Players interfere, and fuck up the ritual, changing their gender as well.
They went for the kingslayer and "fuck this country, we're out" option, rather than just revert the genders of everyone involved, including themselves.
I don't quite understand why the whole party went along with this. 4 guys, playing 2 girls and 2 guys, and a chick playing a guy. At least one of them should have had a pretty good reason for not wanting their character to stay this way.