Plot

While Sheldon is at home in Texas, the rest of the gang decorate for Christmas and think about how much he has affected their lives.

Just as he is about to head to the airport, Sheldon decides to tell his friends that he is going to Texas to fill in for his brother-in-law at his sister's at home baby delivery. With Sheldon away, his friends decide to have a Christmas tree decorating party at Sheldon and Leonard's place. The fact of Sheldon not being there and having a discussion about the movie It's a Wonderful Life (1946), the gang hypothesizes about what their collective lives would have been like if they didn't know Sheldon, most specifically if Leonard didn't move in to Sheldon's apartment. Beyond the fact that many of them wouldn't have ended up even knowing each other let alone those that ended up as couples, each person interjects a little of what they like to think would have happened to each person as each story progresses.—Huggo

Rushing down snow-covered hills, Amy and Penny are video skiing. Amy is winning because her center of gravity is very low. Leonard sprained his ankle playing. Sheldon's sister Missy is about to have a baby & Sheldon is travelling to Texas. Sheldon is going to fill in for his brother-in-law that was in a horrible motorcycle accident.

Everybody minus Sheldon is together for a tree decorating Christmas party. Since Sheldon is absent, so are all of his tree decorating rules (including the required spacing of the ornaments.) Now, both Star Trek and Star Wars ornaments can now be on the same branches. Penny is a little short of funds this year so her Christmas present is going to be giving him herself, which is what Leonard got last year and last night. Stuart then joins them as Amy's computer notifies her of an incoming video chat from Sheldon. His sister has been in labor for an hour and is having a home birth. Sheldon then gets called away to have a family picture taken because his sister is fully dilated and there is no blood yet.

Raj wants to know if Amy would want Sheldon there if she was having a baby. Penny breaks in that she doesn't think Sheldon will be there when they make the baby. Penny wonders if anyone ever considered life without someone. (Leonard: "Knock... knock... knock... What do you think?... Knock... knock... knock... What do you think?... knock... knock... knock... What do you think?" doing Sheldon's Knock.) Amy points out that despite the jokes they make about Sheldon, none of them would be there if it wasn't for Sheldon. None of them would know Amy. Bernadette would never have met Howard. Leonard would not have been dating Penny. Leonard disagrees because he has been going to The Cheesecake Factory for years and he could have still picked her up causing everybody to laugh. Penny then explains what would have happened.

Howard, Raj and Leonard are having a meal and Leonard tells them that he is going to finally ask her out. Penny comes over to ask what they want to eat and Leonard can't even speak to her. He then walks over to her, introduces himself and tells her that there is something he has wanted to ask her for a long time. If she is not too busy he wants to know if she could tell him...where the restroom is.

Back in Apartment 4A, Raj and Howard think that she got the story right. Leonard did ask Penny out, but that could not have happened if he hadn't moved in with Sheldon. Of course, Penny would never have introduced Howard to Bernadette. Howard replies that he could have also met her when she was a waitress.

Bernadette explains her version where she tells Penny that she finds Howard cute. Then she sees Raj feeding Howard a bite of his dessert and then cleaning off his mouth with a napkin and Bernadette changes her mind. Leonard then confronts Penny that she wouldn't have done so great herself due to the type of guys she had been dating.

In Penny's apartment she is preparing food and in walks Zack Johnson who calls her babe. She asks if he paid the rent and instead Zack bought some magic beans.

Sheldon calls back claiming that he has seen lady things that he "shouldn't have seen." According to Amy, they don't normally look like that. Sheldon then says that that is people should not be coming out of people to make new humans. Sheldon's mother calls him to bring a mop. Sheldon is distraught that despite having two PhDs, he is reduced to being the janitor of his sister's birth canal.

Sheldon sends everyone a holiday email including a picture from the birthing room that disgusts Leonard, Penny, and Raj. Penny would still have met Sheldon. Amy describes how without Leonard there, Penny would try and seduce Sheldon.

Penny stalks Sheldon in the laundry room wearing her short shorts. Penny is going to do her dirty laundry, which isn't as dirty as the dirty girl wearing them, who starts to undress and press against Sheldon. Now stripped down to a pink bra, Penny asks Sheldon what he thinks. He finds her a tad asymmetrical, but nothing to worry about. Penny tells him that they are going to do it in the laundry room right now. Sheldon reminds her that he is saving himself for a bespectacled NeuroBiologist who has hair the color of mud as Amy tells the story.

Sheldon calls back from Texas saying that things are going better. His mother asked him to get some towels, so he left and went to "Bed, Bath and Beyond". Amy has now diagrammed the absent Sheldon premise and tells Penny that she would never have met comic book legend Stan Lee. Howard would have always known Raj and Leonard. Leonard never got an apartment with Howard because of the latter's "serious relationship with his mother". Bernadette again mentions that if they had not met, he would still be living with his mother.

Howard tells his version, first he is taking his mother her lunch in her bedroom and that she didn't get enough food. Later he is seen feeding her, but she is still in the bedroom dead reminiscent of the mother in the movie Psycho with Howard now doing her voice. Leonard and Raj did not move in together because Raj thought he was going to be a ladies' man.

In Raj's scenario, Leonard is living with him as Raj cooks dinner for a fat Leonard. Since he had no girlfriend, he compensated by overeating. Then Leonard also makes Raj fat in the living together scenario. Then Stuart shows up (fat) to have dinner with them because he wants to be in someone's story.

In Amy's case, without Sheldon she is alone in her apartment crying over a cupcake and singing "Happy Birthday" to herself. (Happy Birthday to me, Happy Birthday to me. There's tears in the frosting, Happy Birthday to me) Stuart shows up and blows a party favor in her face to be in another story.

Sheldon is back reports that his sister had a baby boy. he finds the baby irritating since he has literally been crying his entire life. Amy tells him to return to be an intelligent role model for his nephew, to which Sheldon agrees. They were amazed that Sheldon did exactly what Amy asked him to do. he has had an impact on Amy too. Amy felt if that were really true she wouldn't still be living alone. Leonard tells her that Sheldon cares for her more than she really thinks. Amy doesn't believe him so he shows that her picture is on Sheldon's screen saver along with Swamp Thing, Madame Curie, Stephen Hawking, etc. Amy gets excited that Sheldon is really into her.

After Sheldon returns, Amy is walking up the stairs and staring at Sheldon. She tells Sheldon that she missed him to which he quotes Han Solo, "I know." Amy also wonders how he felt holding his nephew hoping that he might want one with her someday. He looked into the blank innocent eyes of someone who didn't comprehend anything he said, which he said was like another day at the office for him.

Finally, a fat Raj and Leonard are eating at the Cheesecake factory and again Leonard asks Penny out. She already has a boyfriend, a very suave looking Stuart. Of course, this situation was Stuart's Christmas fantasy.

Title reference: The gang imagines what their lives would be like if Sheldon Cooper was out of the picture.