Sheldon gets a visit from his twin sister, Missy, who seems to be a much more interesting person that Sheldon believes she is. Leonard, Howard and Rajesh all seem to have a crush on her and everyone seems willing to fight for her love. This results in Sheldon deciding to pick out who she will go out with (despite her disapproval), but when the guys finally have enough strength to actually ask her out, they find out she is only interested in one person.