Warning: Spoilers ahead for The Big Bang Theory. Be sure to come back once you've caught up on the show!
The Big Bang Theory is no stranger to guest stars, or guest stars who make multiple appearances as the same character. So, it should come as no surprise that Bob Newhart, who's popped up several times over the course of the series as Sheldon's beloved childhood TV science instructor Professor Proton, would come to the comedy at least once in its final season. That's right, Arthur Jeffries (a.k.a. Professor Proton) came back, this time to help Sheldon and Amy's marriage out when Sheldon made a big mistake regarding his wife. Here's what happened.
Even though Sheldon and Amy are scientists in very different fields, theoretical physics and neurobiology, they've decided to work together on a scientific theory. The newlyweds are very excited about the idea of working together, but it turns out that Sheldon has a lot more time to devote to the project, because it's already a part of his field of study. Amy, on the other hand, has been swamped at work because of the time she took off to go on her honeymoon, and needs to spend much more of her time catching up on her regular neurobiology work than going over ideas for their theory with Sheldon.
As you can probably imagine, Sheldon does not deal well with not being able to discuss his ideas with Amy because she's busy with brain work, which he's always considered a much lower form of science than what he studies. When he comes to Amy's lab to try to talk to her about some new ideas he's had on their theory, and she tells him she can't because she's in the middle of an experiment, he still needs to tell all the information to someone. So, after he tries to get all his excitement out by explaining the whole theory to a very confused Penny, he gets an unfortunate idea that, he believes, is brilliant and the perfect solution to the Amy-has-her-own-work problem.
Sheldon pays a visit to Caltech's president, Dr. Siebert (guest star Joshua Malina), in his office and tells the wary man what he and Amy are working on. Luckily, Dr. Siebert is a physicist, too, so he understands the importance of the theory Sheldon and Amy are trying to put together. When Sheldon can see that Dr. Siebert gets it, he explains that Amy is so busy studying brains that she can't spend much time on their theory, and asks that he find a way to free Amy up so she can commit all her time it.
Even though Dr. Siebert seems skeptical, Sheldon is able to convince him, and when Amy next heads to her lab, Dr. Park is there going over her work. Amy is immediately defensive, pissed and demands to know why he's in her lab messing with her research. As Sheldon walks in saying he's got good news for her, Dr. Park explains that he was reassigned to her project by Siebert, because she was taking a sabbatical to work on something in the physics department. When Sheldon exclaims that that was the good news her had for her, Amy is livid.
So, Amy lets Sheldon have it. She yells at him, saying that he had no right to have her removed from her own project that she's spent so much time developing. She's angry that someone else will be allowed to come in and take over her work, possibly getting to the answers she was looking for without her involvement. When Sheldon responds that she told him she was spread too thin, and he only thought he was helping her lighten her work load, she tells him that he wasn't really helping at all.
The two then find Siebert as he's trying to leave for the day, which does not make him happy, but he gives them time to talk. Amy says he had no right to reassign her research, and then it becomes very clear to Amy that even Siebert thought that this was what Amy wanted. When she asks to have her work given back to her, he says it's not going to be that simple, and she's left even angrier at Sheldon than she was before.
Knowing, as all fans of The Big Bang Theory do by now, that Sheldon does not process these types of conflicts as most people would, no one should be too surprised to find out that the next time we see him, he's having a fitful sleep next to Amy that night in bed. When we go into Sheldon's mind, he's in a deli on Dagobah (yes, an actual inter-galactic delicatessen on a swamp-covered planet) with Arthur's glowy Force Ghost sitting across from him.
After Arthur instructs Sheldon not to order the reuben, Sheldon tells him that he needs help with a problem in his marriage to Amy. He knows he's upset her, but he tells Arthur that he doesn't know how to make it right. Even though Arthur mentions that, when he was alive, he upset his own wife just by getting up in the morning, he's willing to offer Sheldon advice. He says that there are two rules of marriage: don't go to bed angry, and if you don't recognize the shoes under your bed then they're not yours. Sheldon is completely confused by the second rule, assuming that the shoes must be Amy's if he doesn't recognize them, but Arthur tells him to just forget that and stick with the first rule.
When Sheldon snaps awake, he knows immediately that he has to apologize to Amy, but when he wakes her she is not in the mood to talk and tries to go back to sleep. Sheldon then tells her that this is important because they shouldn't go to bed angry, and says he feels terrible about what he did and wasn't trying to hurt her. Amy knows he wasn't trying to be malicious, but he was being selfish, and this leads her to reveal a big fear that she had about marrying him.
Amy explains to him that, while she loves working with him, it's scary for her, because she doesn't want to get lost in this relationship. She was already afraid of the things that are his interests and goals are becoming things that are their interests and goals, meaning that the things that had previously mattered to her would get taken over by Sheldon's enthusiasm for what he loves and she'd have nothing of herself left. So, when he had her taken off of her project, it felt like that was becoming a reality.
Well, with Professor Proton's help, Sheldon was able to realize the massive error of his ways, apologize and make up with Amy. But, this hasn't been the first time he's stepped over the line in a relationship, and it probably won't be the last.