Sheldon can't get a certain tune out of his head. After he realizes the song is about him and Amy, he heads to her apartment. They reconcile and share a passionate kiss in front of Amy's date, Dave. Meanwhile, Howard and Raj find "a" fan of their band, "Footprints on the Moon".
In the middle of the night (0225 hours) Sheldon is documenting his descend into madness on his phone. He needs to urinate, but it is still hours till his scheduled morning urination. He feels he is losing his grasp on reality and may soon forget what a toilet is.
Two days earlier Sheldon and Leonard are in Apartment 4A working on a physics problem. Sheldon is humming to himself though at first he doesn't realize he was humming. After Sheldon knows that he is humming he tries to figure it out and fix words to it. Leonard wants to work telling Sheldon just has an earworm that will disappear. Sheldon keeps working on it, while Leonard asks if they are going to be doing that all night. Sheldon was surprised that he even asked.
Later, Sheldon is on the phone trying to get someone to help him with the tune and is surprised the Rock and Roll Hall of Fame couldn't help him. Penny remarks that everyone gets a song stuck in their head. Sheldon has an eidetic memory and should remember it. He's thinks that there is something wrong with him. Penny told Leonard that if they were patient, he would finally figure that out. Now Sheldon fears that he is starting his descent into madness where he tests the limits of public nudity. That means going barefoot outdoors.
Amy nervously calls Dave asking if he wanted to try going on another date. He is happy to do so especially how he acted on their last date. Amy admitted that they both made mistakes. She took the last bread stick. He gushed over her ex-boyfriend like he was Leonard Nimoy and he was his ex-boyfriend.
Raj is slumming in Howard's lab while Howard is busy working taking about the Department of Outer Space Affairs at the United Nations. Raj had set up a Facebook page for their band, "Footprints on the Moon" which first peeved Howard who thought they were going to make all band decisions jointly. One person comments on their page telling them that their band rocks which excited them.
Sheldon is sitting at his piano playing the tune over and over again. Penny suggests that he take a break. Sheldon's other project is to leave his future crazy self-messages. Music is bad. Penny is his friend and he can accept any food that she gives him, especially since he probably paid for it already.
Bernadette visits Amy discussing her next date with Dave. She tells her that Sheldon turned her down. And that Dave was talking all night about Sheldon which is what Sheldon always did. He promised not to bring him up. Amy is making him dinner which Bernadette says is a big step since it could lead to sex|intimacy. Maybe that's what Amy needs. Bernadette reacts that making her first time with a guy six-foot-seven is like taking her driving test with a bus.
Raj and Howard want to respond to their fan. Raj suggests: We may be "Footprints on the Moon", but you sent us over the moon. Too grandma. Howard wants: Thanks for diggin' our vibe. We'll keep rocking while you keep rolling. They posted it. Their fan's name is Trent Monaco. He's a DJ, brews his own beer, has tattoos and a hot girlfriend.
Penny and Leonard are trying to sleep as Sheldon pays the tune over and over again on his piano. Leonard insists that Penny go deal with it since he had to all day. Penny goes into Sheldon's room to his annoyance and then steals the piano from him. Sheldon wonders why she is so strong. Problem solved. Then he starts playing it on his new tuba.
In the morning, Sheldon is again making videos for his future crazy self. The ideal thermostat set setting is 72 degrees. Then he shows him his spot that he is very protective of. Anyone who sits there show be berated, but in an adorable manner. Also, people are delighted by his love of pranks. To illustrate, he just put something in Leonard's coffee. Then there is his best friend Leonard. Though he does get cranky he can trust him with him with his life. And he does more things for him than he can even count. Leonard thanks him.
Raj and Howard are checking Trent out on the Internet. Bernadette reminds them that they only played together once. And at a children's hospital until they were asked to leave. Raj finds out that he is at a coffee shop and both of them what to meet him. Bernie thinks that they are stalking him; which they were.
Their date starts well as Dave enjoys her meal since he usually doesn't get many home-cooked meals. His former wife wasn't much of a cook until she started cheating on him with the chef. Dave wonders how long she'd live there. About five years though she was thinking of moving to a better place now that she didn’t have to be close to... She stopped and apologized for bringing him up. Dave was pretty excited to find Sheldon lived nearby. Amy also mentions that he didn't drive so she had to take him everywhere. Dave changes the subject and ask where she got her neat model train from.
Sheldon, Leonard and Penny are having dinner as Sheldon continues to play the tune including gargling it. Sheldon asks them if they had ever had anything that was so relentlessly irritating. Leonard asks Penny if that’s a trick question. Sheldon then lists some scientific geniuses that were crazy. He follows with other notable people like Van Gogh, Pollock, Bobby Fischer, Brian Wilson of The Beach Boys…Something clicks in Sheldon’s brain and he realizes the song is "Darlin'" by The Beach Boys. He is greatly relieved that he is not crazy.
Raj and Howard are at the coffee shop observing Trent who is listening to music on his laptop. Raj wants to go up to him, but Howard thinks it would be cooler if he discovered them. Can you imagine if he was listening to their music and then saw them? The guy's euphoria dies when they see Trent picking his nose and that didn't bother them. But eating it, that is too much to bear. While they make a hasty retreat, Trent did recognize them, but they denied it.
Sheldon is listening to the song and wonders why he was stuck on that one. Penny asked him if he even liked The Beach Boys. Sheldon reminds her that they had the word “beach” in their name. Leonard gets Sheldon to focus again on their physics problem until Sheldon does realize why it was that song. It was about Amy and how she made his life better. Checking out the lyrics he finds the following: "I was living like half a man, then I couldn’t love, but now I can, You pick me up when I’m feeling sad, More soul then I ever had." She did soften him. Both Leonard and Penny agree with him. Sheldon calls Amy the dryer sheets of his heart and then goes to see her. Leonard asks Penny if he is the dryer sheets of her heart. Better. He’s the lint trap of her love.
Amy and Dave are awkwardly sitting on the couch. Amy leans over to admire Dave’s tie pin. He leans in and kisses her. Amy jumps back. She is a bit nervous, but they are on a date so they try again. As they approach each other, Sheldon knocks on the door. Dave is excited as Amy goes to answer the door. She tells Sheldon that it’s not a good time. Sheldon says he doesn’t care and that he had a song stuck in his head that he couldn’t get out. The song was about her and he can’t get her out of his head. Amy is like that ear-worm, but is in his heart. She is his heart worm, but not the poodle killing kind. Amy doesn’t understand. Dave jumps in saying, "If I may, I believe what he is saying in a charming and delightful way is that he loves you wants you back.” Amy is stunned as Sheldon realizes that she is on a date. Amy wants him to continue. Sheldon tells Amy he wants
to be her boyfriend again and that he loves him her. Amy finally breaks into a e at each o and tells him she loves him too. Sheldon smiles as they stare at each other until Dave pokes his head around the door again and cries "KISS HER, YOU BRILLIANT FOOL!" Sheldon and Amy then embrace and begin to kiss. Sheldon eventually pulls away and apologizes for interrupting the date, but Amy pulls him back and they embrace in another passionate kiss.
Finally, as Sheldon and Amy have not stopped kissing, Dave walks out telling them goodnight. Amy kicks the door closed as they continue. Dave still wants to meet Sheldon later to discuss physics and all in all considers it a lovely evening.
- Title Reference: The song that Sheldon can't get out of his head is like Amy whom he can't get out of his heart.
- Taping date: November 10, 2015
- This episode was watched by 15.27 million people with a rating of 3.8 (adults 18-49).
- Total viewers including DVR users 21.47 million.
- The Big Bang Theory was ranked #3 for the week ending December 13, 2015.
- This episode aired in Canada on December 10, 2015.
- In the United Kingdom, this episode aired on Thursday, December 24, 2015.
- Chuck Lorre's vanity card 
- Episode transcript 
- Guest starring:
- Teleplay: Steven Molaro, Steve Holland & Jeremy Howe
- Story: Eric Kaplan, Jim Reynolds & Saladin K. Patterson
- Jesse Schedeen of IGN - This week's Big Bang Theory more or less wrapped up the big Sheldon/Amy conflict that's been running since the Season 8 finale. Apparently, the writers felt they've taken the breakup about as far as it can go. That's certainly debatable, but for a show that's never been big on serialized storytelling, it's impressive the conflict lasted as long as it did. The big Sheldon/Amy reunion helped prop up what was otherwise a pretty uneven installment. 
- This episode was really adept at conveying just how annoying Sheldon can be when he really fixates on something. That proved to be both a good and bad thing. It was certainly easy to sympathize with Leonard and Penny as they were subjected to hour after hour of Sheldon humming the same seven-note tune and fretting about losing his mind...But at the very least, this story line had a satisfying resolution once Sheldon realized that his lingering desire for Amy was the root cause of his distress. Even if this status quo could have lasted a few more weeks at least, both Sheldon and Amy have gone through the necessary character growth by now. Private review.
- Sheldon and Amy get back together - episode 10 is the 4 year anniversary of the season 5 episode "The Flaming Spittoon Acquisition" (S5E10) when Sheldon interrupts Amy's date with Stuart and asks her to be his girlfriend. Second time Sheldon interrupts Amy's date to advance their relationship and Amy never minds the interruption.
- Stephen Merchant returns as Dave.
- The first time Sheldon and Amy passionately kiss (proper making out) and arms wrapped around each other, a huge step in their relationship.
- Another first time for Sheldon and Amy is that they both profess their love for each other, Sheldon saying "I love you." then Amy replying "I love you too." They have professed their love for one another before, but individually in separate episodes.
- When kissing Dave, Amy calls herself silly just like she and Sheldon called her on their aquarium date in the last episode. This may be a revelation to Amy that she is not as serious as she thought she was and that she is closer to the childishness of Sheldon making them even more soulmates.
- When Sheldon finally recognizes the name of the song, the scene shows a fast forward motion into his brain through his eye. The zoom-in through the eye is a reference to the "I'm having a vision" scene in "That's So Raven", while the brain scene refers to the famous "brain blast" from the "Jimmy Neutron" franchise.
- Amy's date Dave reveals that his last name is Gibbs.
- Bernadette only appears in two scenes in this episode.
- Sheldon quips about Penny still freeloading food from him, even though she became financially independent.
- Bernadette shares no scenes with Sheldon, Penny and Leonard in this episode.
- Amy shares no scenes with Penny and the three other guys (Howard, Leonard and Raj) in this episode.
- Raj and Howard only share one scene with Bernadette in this episode and they both share no scenes with the other two men (Sheldon and Leonard) and the other two girls (Amy and Penny) in the rest of this episode.
- Sheldon plays the "Darlin'" tune on a piano in two scenes - in real life, Jim Parsons is a talented piano player.
- Amy: Sheldon, this-this isn't a good time.
- Sheldon: I don't care. Amy, there was a song I couldn't get out of my head. Eventually, I realized the song was about you, and like that earworm, I can't get you out of my heart. So, what I'm trying to say is, you're my heartworm. (Amy looks shocked for a second) The metaphorical kind, not-not the poodle-killing kind
- Amy: (stammers) W-W-W-What?
- Dave: If I may... I believe what he's saying, in a charming and delightful way, is that he loves you and wants you back. (shakes Sheldon's hand) Dave Gibbs, huge fan of your work. Oh. Don't mind me.
- Sheldon: I'm-I'm sorry; I didn't realize you were on a date.
- Amy: No, it-it... it's okay. Keep going?
- Sheldon: Amy, if you want to be my girlfriend again, I really want to be your boyfriend.
- Amy: I really want that, too.
- Sheldon: Good. Because I love you.
- Amy: (she finally smiles) I love you, too.
- Dave: Kiss her, you brilliant fool!
- [Sheldon slowly approaches Amy and pulls her into a tight embrace and passionate kiss].
- Sheldon: (After kissing Amy) Well... I'll let you get back to your date.
- [Sheldon exits and Amy now pulls his arm]
- Amy: Get back here!
- [Amy pulls Sheldon back into a tight embrace. They both kiss each other again just as "Darlin" by the Beach Boys plays in the background and finally the screen fades to black]
- (The ending scene at Amy's apartment where Amy and Sheldon are still embracing and kissing passionately)
- Dave: Okay, then. I'll, uh, see myself out. Amy, thank you for dinner. Dr. Cooper, pleasure to meet you, sir. Uh, if perhaps sometime you have a spare moment, I'd, uh, love-love to discuss physics, or "shoot the breeze," as you Yanks say.
- (Amy kicks the door closed on Dave while she's kissing Sheldon).
- Dave: Ah. What a lovely evening.
- [He has now left the hallway]
- (The scene of Amy's apartment where Bernadette is having conversations with Amy about Dave)
- Bernadette: So, you're really going out with Dave again?
- Amy: Why not? He's actually a very nice guy.
- Bernadette: But he spent an entire date talking about how much he loves Sheldon.
- Amy: That's nothing Sheldon hasn't done before. (she puts a plate of brownies down onto the table furiously) Dave's just a big fan of his work. (she now sits with Bernadette on the couch) Besides, he said he wouldn't bring it up again.
- Bernadette: Okay. So where's he taking you?
- Amy: Oh, he's coming here. I'm actually making dinner.
- Bernadette: Oh. That's a big step.
- Amy: It is?
- Bernadette: Yeah. You're inviting him into your home. It's intimate. (she whispers sarcastically to Amy) It's where your underpants live.
- Amy: You know what? Good. I tried to get back together with Sheldon; he shot me down; Dave likes me. Maybe intimate is what I need.
- Bernadette: (she's so confused by all of this) You sure? You've never really been with a man. Do you really want to start with one that's six-foot-seven?
- Amy: Why not?
- Bernadette: (she's a tiny bit disgusted) 'Cause it's like taking your driver's test in a bus.
- (Amy thinks for a little bit)
- [The scene at the living room of the Wolowitz house]
- Howard: Look at this, Trent is rebuilding a vintage motorcycle.
- Raj: Hmm. That is so cool! Old broken things are so much better than new things that work.
- Bernadette: Who's Trent?
- Howard: Oh, he's our fan.
- Bernadette: Fan of what?
- Howard: Uh... (laughs) Did you forget? We're in a band.
- [Raj shakes his head for a second]
- Bernadette: (1st time: she's asking both men crossly) You mean because you played one time in the comic book store?
- Howard: And at the children's hospital until they asked us to leave.
- Raj: Hey, dude, Trent just checked in at the coffee shop on Fair Oaks.
- Howard: Really? You want to go down there and meet him?
- Bernadette: (2nd time: she's asking both men crossly) Are you stalking him? That's creepy.
- Raj: It's not creepy. I built a Footprints on the Moon fan page, Trent joined it.
- Howard: After that, all I did was check out his profile, go back in the archive of his feed until I found his Twitter handle.
- Raj: From there, it was easy to find him on Instagram, Snapchat and pretty much track his every movement.
- Howard: So if you think that's creepy, you married the wrong guy.
- Bernadette: (she is now very cross) Maybe I should marry Trent.
- Raj: Yeah, like she could get Trent.
- [Bernadette looks down crossly at the insulting thing that Raj had said].
- (The scene of Amy's apartment where Amy and Dave are seen having dinner)
- Dave: This is delicious.
- Amy: Thank you.
- Dave: Been a long time since I had a home-cooked meal.
- Amy: When you were married, did your wife cook?
- Dave: Not at first, no. But when she began cheating on me with a French chef, she became quite the wiz in the kitchen.
- Amy: So, a little silver lining.
- Dave: I suppose. Yeah. Nothing takes the sting out of a shattered life like a properly-seasoned bowl of onion soup. How long have you, uh, lived here?
- Amy: About five years. I'm actually thinking of moving to a better place now that I don't need to be so close to... Well, you know.
- Dave: I do. The brilliant physicist that I now know lives in the area, not that I care.
- Amy: Yeah. Anyway, he doesn't drive, so, I pretty much had to take him everywhere.
- Dave: Had to or got to? Sorry.
- Amy: My fault. I brought him up. Yeah.
- Dave: Well, let's change the subject. No more mentions of you-know-who.
- (Amy laughs)
- Dave: That's a cool train. Where did you get that?
- (Amy bows grumpily at Dave's question)
- Amy: That's an interesting tie clip.
- Dave: Oh, thanks. It's, uh, Avogadro's constant. It's useful for calculating the number of atoms in a substance, or causing regret in anyone who asks about it.
- Amy: Oh, I... I think it's neat. Oh!
- Dave: Sorry. Sorry. No one's ever liked the tie clip before, so I just lost all control. I...
- Amy: No, it... it's okay, and we are on a date. I'm... I'm just a little nervous.
- Dave: Well, no need to be nervous with me. I'm just a harmless giant from a foreign land.
- Amy: You know, I'm just being silly. I... I don't know what I'm waiting for.
- Sheldon: (knocking) Amy? (knocking) Amy. (knocking) Amy?
- Amy: That's Sheldon.
- Dave: You're kidding! How's my hair?
- Sheldon: Well, I’m not everybody. I have an eidetic memory, but I should remember what that song is, but, I can’t. Something’s wrong with me.
- Penny: I told you if we were patient He’d figure it out for himself.
- Amy: Yeah, well we both make mistakes, you know. I took the last breadstick, you gushed over my ex-boyfriend like he was Leonard Nimoy and you were my ex-boyfriend.
- Sheldon: This is Leonard. He’s your best friend in the world.
- Leonard: All right, just stop. This is ridiculous.
- Sheldon: Sometimes he gets cranky, but you can trust him with your life. And he does more things for you than I can list.
- Leonard: Thank you.
- Sheldon: Have you ever dealt with something that was so relentlessly irritating?
- Leonard: That’s a trick question. Right?