The Big Bang Theory S06E19 - Penny, Amy & Bernadette manage to get Sheldon to tell a secret.

At Penny's apartment the girls are having wine, while Penny can't believe that he burned the letter. Bernadette explains that he already had a tough day since he accidentally worn her pants to work and they were bigger on him than her. Amy is curious about what was in it. They could ask Sheldon since he read it. Bernadette doesn't want to ask since she doesn't want in invade her husband's privacy. Penny says that she could ask Sheldon while Bernadette was in the room. She quickly said, “That works.“ and th