The Big Bang Theory - Season 4 Episode 5 HD

The Desperation Emanation Sheldon goes down the stairs... singing the names of the closest stars. Sheldon has been hiding from Amy, because he thinks she wants to become his actual girlfriend, since she asked if he would be willing to meet her mother. And, when he told the mailman his story, he answered "Got your back, Jack. Bitches be crazy". Thus, the last sentence.