The Big Bang Theory, a sitcom centered around four nerdy scientists, has been on the air for six years. The show is well-loved by the audience and has become a mature comedy. The honest and slightly dull Leonard (Johnny Galecki) and his beautiful girlfriend Penny (Kaley Cuoco) have a stable relationship, but they never touch on the big issue of marriage; Sheldon (Jim Parsons) is a big weirdo, everyone loves him, and of course, his biologist girlfriend Amy loves him the most; Howard and his wife Bernadette live a happy life; and Raj finally manages to talk to women without alcohol, but he is still single. When will his spring come?