3rd Rock from the Sun - Season 4 Episode 10 : Two-Faced Dick 2001

After three years, the Big Giant Head has finally accepted Sally's request to have her body changed for a man's. For their convenience, the bodies of Dick and Sally are switched. Now, in each other's bodies, Dick and Sally must try and maintain each other's romantic relationships and get accustomed to the changes that their new gender brings, while waiting for their request to be switched back to be accepted. Meanwhile, Harry is left in charge of Happy Doug's when Doug goes on vacation, but becomes worried when a group of burly, tough-looking bikers arrive.