Die Geschenk-Hypothese

The boys are sitting in the cafeteria. They are having a discussion about how Superman cleans his suit. However Raj, Howard and Leonard can't touch Sheldon's logic. Then David Underhill comes in: He has received the MacArthur Fellowship. With his observation of high-energy positrons, he has done important work, and rendered Leonard's practically worthless. David comes to Leonard and asks him for help with his photo electron multiplier.

Leonard is gladly at his disposal.

The boys are playing Wii bowling when Leonard comes home. Sheldon is offended that Leonard has skipped their game night. Yet Leonard was at David Underhill's place and was working with him. He is greatly impressed by this colleague, and they are indignant that he apparently finds him more interesting than his friends.

Penny comes in and inquires whether Sheldon has put up a Christmas tree. But Sheldon states clearly that they don't celebrate it. But when Penny announces that she has gotten presents for both of them, Sheldon is upset. He now feels under pressure to give her something. And it must be equal in value to Penny's present. Sheldon wants to go to the mall right away.

Leonard strains to go up the stairs with David's help. In an attempt to ride David's motorcycle, he has fallen. Penny comes over and helps David bring Leonard upstairs. At the same time they both get to know each other better and David also invites her into the laboratory. Leonard pretends to be uninterested in front of David.

In the shopping center Raj, Howard, and Sheldon are looking for a present for Penny. But Sheldon isn't happy with anything. They recommend a bath item, but Sheldon is skeptical. He doesn't know how big a gift basket he needs to get for it to be an appropriate present.

David and Penny are enjoying themselves in the cafeteria, when Leonard arrives. She plays the physics enthusiast. Leonard urges him to work but David takes the afternoon off for Penny.

Leonard lies on the sofa, as Sheldon, Raj, and Howard return from shopping. They have multiple baskets in different sizes, and Sheldon has a perfect plan. He wants to open Penny's present first and then choose the right size of basket to present to her.

Leonard knocks at Penny's door and wants an explanation. He doesn't understand, why Penny wouldn't go out with him because of his intelligence, and yet would flirt with David. However, Penny has already reformed. David is married! They both agree and wish each other Merry Christmas.

Penny comes to the apartment and wants to bring her presents. Sheldon is nervous, when he opens the present. In the package there is a napkin. It is personally signed by Leonard Nimoy. When Sheldon understands that he had wiped his mouth with the napkin and that he now possesses the DNA of Leonard Nimoy, he is over the moon. He runs next door. Meanwhile, Leonard receives his gift from Penny - Motorcycle lessons. He himself gives Penny a science quiz.

Now Sheldon returns. He has all of the gift baskets with him and fears that they are still not enough to equal the value of the napkin. He hugs Penny.