Big Bang Amy Takes Charge - S1:e12

Sheldon has just earned a black eye courtesy of Penny's boyfriend learning that she's been screwing around with the geek. Penny tries to nurse Sheldon's wound, but she is interrupted when Amy knocks on the door. She doesn't know that Sheldon is there, so Penny tells him to hide. It turns out that Amy is here to take Penny to the comic book convention and has come complete with a skintight outfit for each of them to wear. As Sheldon watches, the girls each strip naked and put on their outfits. He makes his presence known just in time for Amy to hustle them both out of the door. Later, when they return from the convention Amy lets Sheldon know that he looks rugged with his back eye and gives him a long kiss to prove it. Amy is also into the way Penny looks in spandex, so she shoves Sheldon down on the couch to give Penny an equally passionate kiss. Sheldon whips his cock out to stroke it as he watches the girls make out, and when Amy notices she gets on her knees and starts sucking to sh