- SpongeBob SquarePants
- Squidward Tentacles
- Eugene H. Krabs
- The Sonars (heard only)
- DJ (heard only)
- Gary the Snail
- Martha Smith
- Frankie Billy
- Harold "Bill" Reginald
- Abigail Marge
- Fred (blue)
- Nat Peterson
- Frank (red shirt)
- Jimmy Gus
- Frank (lifeguard)
- Sandy Cheeks
- Norma Rechid (cameo)
- Paco (cameo)
- Scooter (cameo)
- Gus (cameo)
- Patrick Star
- Earworm (debut)
SpongeBob is shown at the Krusty Krab during closing time with Mr. Krabs and Squidward. He is in the kitchen and starts singing a song. Squidward gets annoyed by SpongeBob's singing. Mr. Krabs comes and says to mop the floor. Squidward tells SpongeBob again to stop singing and then puts on the radio, but it's playing "Musical Doodle" - SpongeBob picks up the radio and starts dancing and singing to it. After it ends, SpongeBob sighs happily. Afterwards, Mr. Krabs says it's closing time again and Squidward runs out saying "Freedom!" SpongeBob is sitting down on a table, singing to the song and Mr. Krabs yells his name.SpongeBob floats out of the Krusty Krab and lands outside a Record Shop. He hears "Musical Doodle" playing. He then buys the record and goes home, opens up Gary's shell, revealing a record player, and plays the song until bedtime. SpongeBob says "Come to bed when you feel like it." He goes to sleep but then starts whistling the song. He goes back downstairs to listen to the song again.
He is then shown at the Krusty Krab the next day, looking very tired. Mr. Krabs warns him to get to work. Mr Krabs hears SpongeBob singing the "Musical Doodle." He is warned to stop singing that song again, but finds it very hard not to. He hands out Krabby Patties while singing the song, annoying the customers in the process. Mr. Krabs comes out of his office to see what's wrong. All the customers blame SpongeBob for annoying them. Mr. Krabs warns SpongeBob once again to stop singing the song or else he will send him home. In the kitchen, SpongeBob's eyelids form into mouths and start singing the song - the same thing happens with his back.
In the next scene, the kitchen is shown absolutely wrecked, with "doodle" written on the walls and everything else wrecked as well. Also, there are condiments and patty batter all over the wall. After Mr. Krabs tells SpongeBob to leave, the latter seems that he has completely lost it.He goes home while singing the song - Sandy, Mr. Krabs, Patrick, and Squidward follow him, tie him to a chair, and gag him. Sandy explains that he has an "earworm" - an infection in which someone is stuck on a catchy song and is unable to stop singing; the more the person sings the song, the more infected and stronger the infection gets and more crazier the person gets. Mr. Krabs wants to just pull the earworm out but Sandy says that they can't do that or else it will damage SpongeBob's brain and it can only be cured if another song gets stuck in their head. Mr. Krabs sings a sea-shanty and Sandy sings a Western song, but none succeed. Sandy says "someone with musical talent" can cure him (in this case, Squidward). Squidward starts playing his clarinet. The earworm gets annoyed and leaves. Squidward is then shown in bed, praising himself. The earworm comes and goes into Squidward, and now the latter has the earworm and is humming his song. Squidward then screams loudly as the episode ends for unknown reasons, inferring he probably found out he caught the earworm.
|( ‣ ) Associated production music|
|( • ) Original music|
|( ◦ ) SpongeBob music|
‣ SpongeBob History Song - Nicolas Carr, Sage Guyton, Jeremy Wakefield [Title card]
‣ Steel Sting - Jeremy Wakefield [Squidward groans]
‣ Salty Squid Jig - Nicolas Carr, Sage Guyton ["What are you doing? It's closing time!"]
‣ Steel Sting (k) - Jeremy Wakefield [Squidward cleaning the cash register]
‣ Comic Walk - Nicolas Carr [SpongeBob mopping the floor]
• Musical Doodle - Casey Alexander, Zeus Cervas, Eban Schletter [Plays on the radio]
‣ Krusty Krab Tango - Steve Marston [Squidward quickly leaves]
• Musical Doodle - Casey Alexander, Zeus Cervas, Eban Schletter [Plays on the radio]
‣ Krusty Krab Tango - Steve Marston [SpongeBob leaves the Krusty Krab]
‣ ? [Harp music as SpongeBob floats]
• Musical Doodle - Casey Alexander, Zeus Cervas, Eban Schletter [Plays on a record]
‣ Shellfish Behavior - Sage Guyton, Jeremy Wakefield [SpongeBob comes home]
• Musical Doodle - Casey Alexander, Zeus Cervas, Eban Schletter [Plays on record]
‣ Hawaiian Link (b) - Richard Myhill [Gary sleeping]
‣ On the Beach - Kapono Beamer [SpongeBob goes to bed]
‣ Vibe Sting - Nicolas Carr [SpongeBob's eyes open]
‣ Lap Steel - Nicolas Carr ["Oh, fine. I'll just listen to it one more time to get it out of my system."]
• Musical Doodle - Casey Alexander, Zeus Cervas, Eban Schletter [Plays on record/Plays repeatedly]
‣ Another Krusty Krab Day - Michael Bolger, Nicolas Carr [the next day]
‣ Tension Bits - Nicolas Carr, Sage Guyton, Jeremy Wakefield ["SpongeBob, wake up!"]
‣ Another Krusty Krab Day - Michael Bolger, Nicolas Carr [bucket of patties]
‣ Steel Licks (e) - Jeremy Wakefield [SpongeBob laughs nervously]
• Musical Doodle - Casey Alexander, Zeus Cervas, Eban Schletter [Plays again/Plays again]
‣ Harp Ding - Nicolas Carr ["That's it!"]
• Musical Doodle - Casey Alexander, Zeus Cervas, Eban Schletter [SpongeBob singing/SpongeBob annoying customers]
‣ Danger HQ - Norman Dane [Krabs wakes up]
‣ In a Minor Mood Jig - Michael Bolger, Nicolas Carr ["Me customers!"]
‣ Sailor's Sting 7 - Michael Bolger, Nicolas Carr [Krabs tells SpongeBob to stop singing]
‣ Sailor's Sting 15 - Michael Bolger, Nicolas Carr [SpongeBob trying not to sing]
‣ Tragic Bridge 2 - Phil Green [SpongeBob going nuts]
‣ Agitation Bridge 3 - Phil Green ["What in blazes are you doing?"]
‣ The Shock - Dick de Benedictis ["Trying to escape is futile!"]
‣ Mutations (a) [#53] - Trevor Duncan [SpongeBob crawling home]
‣ Shock - Cornelus Joh Bolten [SpongeBob on the ceiling]
‣ Lonely Stranger - Laurie Johnson ["Just as I thought."]
• Musical Doodle - Casey Alexander, Zeus Cervas, Eban Schletter [Earworm listening "Musical Doodle" inside SpongeBob's head]
‣ Danger Man 2 - Norman Dane ["Let's just rip the little sucker out."]
‣ The Irish Washerwoman - Nicolas Carr [Krabs' sea shanty]
• Musical Doodle - Casey Alexander, Zeus Cervas, Eban Schletter [Earworm still listening "Musical Doodle"]
‣ Steel Sting (v) - Jeremy Wakefield ["I'll be darned if anyone can resist a Western song while wearing a Western hat."]
• Musical Doodle - Casey Alexander, Zeus Cervas, Eban Schletter [Earworm wearing a Western hat]
• Life on the Prairie - Casey Alexander, Zeus Cervas, Eban Schletter [Sandy sings]
‣ Steel Sting (p) - Jeremy Wakefield ["That only seems to have made him madder."]
‣ ? - Nicolas Carr, Barry Anthony [Squidward playing clarinet]
‣ Skipping to School - Sage Guyton, Jeremy Wakefield [SpongeBob is cured]
‣ Hawaiian Happiness - Jon Jelmer [Squidward goes to bed]
‣ ? - Nicolas Carr, Barry Anthony [Ending]
- This episode is available on the Complete Seventh Season, SpongeBob on Tour, and Next 100 Episodes DVDs.
- As of January 30, 2017, The Internet Movie Database (IMDB) gives this episode a rating of 7.8/10 based on 104 ratings by users. TV.com users give this episode a rating of 8/10 based on 93 votes.
- This episode was originally going to premiere with "Buried in Time," as said from a brief crew meeting in August 2010, but was paired up with "The Abrasive Side" instead.
- The song SpongeBob bought was on a record instead of a CD or a digital download like it would be in modern times.
- The title card background is identical to that of "Bubblestand," except the letters are written in pink and there are no bubbles.
- This is the second appearance of Gary's record player. The first was "Your Shoe's Untied."
- The Gary clock from "Procrastination" appears again.
- The song lyrics match what happens in the episode. For example, "The song you escaped from is back again! You wonder if the madness will ever end! Trying to escape is futile! So just listen now to the Musical Doodle! Listen again to the Musical Doodle!"
- Sandy said they couldn't rip the earworm out or it would damage SpongeBob's brain. However, she stuck her hand all the way into SpongeBob's head and put a hat on the earworm, nearly touching the brain.
- To prevent anyone else from getting infected by the earworm, they could have just squished it before it infected Squidward.
- Sandy mentions the episode title when she says "You're suffering from a condition known as Earworm. You see, when your brain becomes stuck on a catchy tune, you're spectacle with Earworm infection and you've got a nasty one there."
- This episode premiered in the UK four years after "Wigstruck" premiered.
- This episode premiered 10 years after the premiere of "Mermaid Man and Barnacle Boy III" and "Squirrel Jokes" and one year after the premiere of "Greasy Buffoons" and "Model Sponge."
- The Earworm enters Squidward's brain at the end of the episode, this could presumably be its revenge for Squidward causing it to leave SpongeBob's brain.
- This episode is similar to the Dexter's Laboratory episode "Head Band." In it, Dee Dee and co. have a song stuck in their heads, thanks to a microscopic boy band in their ears. The song finally ends when the band breaks up.
- "Earworm" is different, in that only SpongeBob gets a song stuck in his head and the culprit is in his brain, not his ear.
- The scene where SpongeBob writes letters on the wall is a reference to the 1980 movie The Shining, where Jack Nicholson's character, Johnny, writes "all work and no play makes Jack a dull boy" on the walls of the hotel.
- The ending is similar to the 1973 movie The Exorcist, like when SpongeBob crawls like a spider around his house and then inside the window.
- One of the faces SpongeBob makes as he goes insane looks similar to some of the faces Ren Hoek of The Ren & Stimpy Show has made.
- Earworm is a real-life condition in which a song plays over and over in one's head. Like in the episode, a commonly used cure for earworm is to play another catchy song.
- Mr. Krabs' song can also be heard in the 1951 Tom and Jerry cartoon film "Jerry's Cousin," although without vocals and slightly higher pitched.
- Usually SpongeBob's brain is pink, but in this episode, it is blue.
- Typically, one's eardrum prevents them reaching to their brain through their ear alone. Though, it is possible that sponges don't have eardrums (hinted in "Blackened Sponge," even though SpongeBob has an eardrum in "The Inside Job").
- After Mr. Krabs tells SpongeBob to stop singing, his eyelids turn a paler red for a second.