The Big Bang Theory Season 2 Episode 11 : The Bath Item Gift Hypothesis
Sheldon worries about the approaching Christmas holidays and his indecision on what present to get Penny. After deciding on a basket of bath items, he discovers a wide selection available; unsure of what Penny is going to get him and what he should get her in return, he buys an entire array to cover all contingencies. Penny's gift to Sheldon is a napkin both autographed and used by Leonard Nimoy. Sheldon is overwhelmed since he now possesses his DNA and can grow his own Leonard Nimoy. He responds by giving Penny all the gift baskets and then a rare "Sheldon" hug.