When an Ear Worm gets into Sheldon's head, he spends days going crazy trying to remember the song, leading to a big revelation. Amy has Dave over for a dinner date, against Bernadette's warning that it's a big step, and the relationship could become intimate. Howard and Raj's filk band have a fan.
- Apocalyptic Log: Sheldon records messages to his future self when he fears he's going mad.
- "Awesome McCool" Name: Trent Monaco.
- Big Damn Kiss: The biggest yet.
- Bigger Is Better in Bed : Discussed, although in a veiled way. Dave is 6'7". A certain amount of Fridge Logic suggests Bernadette had some experience, with Glenn (who is nearly the same height).That's like taking your driver's test with a bus.
- Broken Pedestal: Howard and Raj become obsessed with Trent, to the point that they go to the bar hoping that he would recognize them and become friends. Then they see him picking his nose. And then eating the booger. They beat a hasty retreat.
- Confession Cam: We open on Sheldon talking into a camera. Subverted, in that his only reveal is the need to urinate.
- Continuity Nod: Penny's abnormal strength, and Sheldon's rule that no one is allowed in his room (especially girls). Also the temperature of the apartment, which has to be 72 degrees.
- Once again, Sheldon decides to upgrade his relationship with Amy while she's on a date with another man.
- Dissimile: Sheldon calls Amy his fabric softener, and his heartworm.The metaphorical kind, not the poodle-killing kind.
- Ear Worm: An in-universe example, which also provides the episode's title. Sheldon tries to sing several songs to the melody, but none of them work. This frustrates him because he has a Photographic Memory.
- Eureka Moment: Sheldon starts talking about geniuses who went mad, and gets to Brian Wilson, which triggers his memory and realizes that the song he's been humming is "Darlin'" by The Beach Boys.
- How We Got Here: The episode opens on one of Sheldon's messages, announcing "Day two of my descent into madness". Then we cut to two days earlier when Sheldon first hums the song that supposedly triggers said descent into madness.
- Hufflepuff House : Sheldon gives Leonard a "point to Hufflepuff."
- I Ate WHAT?!: Along with a bit of Noodle Incident.Leonard has no idea what I put in his coffee. It's not Folgers Crystals, I can tell you that.
- Incessant Music Madness: Sheldon drives Leonard and Penny crazy humming the song to figure out where it's from. When he plays it on the keyboard late at night, Penny goes into his room and takes away the keyboard. Unfortunately, Sheldon has a tuba.
- I Want My Beloved to Be Happy: Sheldon to Amy, Dave to Amy and Sheldon.
- Journey to the Center of the Mind : We get to see the synapses firing, when Sheldon figures out the Ear Worm.
- Loony Fan: An inversion. Trent likes Footsteps On The Moon. They stalk him. A mild example in Dave's admiration of Sheldon's work.
- Love Triangle: Amy, Dave, and Sheldon. A very strange example, in that Dave is a huge fan of Sheldon's. He actually cheers for Amy and Sheldon to get back together and leaves happily when they do.
- Nose Nuggets: Howard and Raj run away when they see Trent doing some mining...
- Pretty Freeloaders: Lampshaded with regards to Penny:Sheldon: This is Penny. She is your friend. If she offers you food, it's safe to take it. You probably paid for it anyway.
- Race for Your Love: Sheldon after his epiphany.
- Science-Related Memetic Disorder: Discussed. Sheldon points out how geniuses in all fields are often insane.
- Shout-Out: To several songs, including "Footloose," "Respect," "The Star-Spangled Banner," and the theme for SpongeBob SquarePants. And The Beach Boys.
- Your Cheating Heart : Dave's ex-wife was cheating on him with a chef, and became a better cook for it.