- The full version of the main Theme Tune, AKA "BoJack's Theme" by Patrick Carney, used at the beginning of each episode, is an epic work of jazz music, with its seamless smooth façade of blues rock often giving leeway to a melancholic saxophone and beats that oscillate both moods to instill a creeping sense of chaos, urgency, dread, rhythm, energy and resigned numbness, fittingly putting you inside the mind of the very screwed-up horse, all ready to watch his long descent into spiritual hell of the episode.
- While the full version of "BoJack's Theme" is awe-inspiring as it is, the shorter version for the opening sequence is a feast for all senses, a blend of visual and musical genius: from bed to the supermarket/studio/cinema/hallucination to party-crashing to pool-dunking, the stare BoJack gives at the viewer while the rest of the world moves faster and faster and the music builds to a crescendo onto the saxophone transition as he sinks into his pool while everyone is watching him, the way the catatonic horse oddly connects with the audience in this general feeling of helplessness. It's your own very personal Heroic BSoD.
- The Ending Theme song, "Back in the '90s" by Grouplove, which describes Bojack's melancholy mood from a self-reflective first-person viewpoint, and is also very hard to get out of your head.
- "Three Little Orphans", the theme song for the Show Within a Show Horsin' Around. While it is cheery sitcom music, it still sounds so hauntingly nostalgic, serving as a great contrast to Bojack's depressing life outside the show.
- "Who's That Dog?", the theme song of the other Show Within a Show Mr. Peanutbutter's House, which also doubles as Peanutbutter's catchy phone ringtone.
- The Generic Songs, which serve as funny meta-gags about older music from the 1980s, 1990s, and 2000s. Season 4 briefly gave us "The Gals of '44" and almost gave us one for 1999, but Hollyhock stopped BoJack's flashback before we got it.
- This episode features a weirdly funny pop song of the same name by Sarah-Lynn.
- Later on, there's "On Fire Again" by Circuit Shaker, booming all over BoJack's house during Sarah-Lynn's Wild Teen Party.
- Lyla Foy's "Impossible" is perfect for the melancholy ending dedicated to Princess Carolyn, especially when it begins at the edge of the series's Cerebus Syndrome with three lines:
- Death Grips' "No Love" plays during Bojack's drug binge, which only adds to the disorganized Mind Fuck of his self-discovery journey into his troubled psyche, kicking intermittently between hallucinations until it kicks into overdrive when BoJack is running through a wrinkled paper, with stop-motion techniques similar to Rejected, mixed with desperate pencil scribbles that sound like nails on a chalkboard.
- "Wild Horses" by The Rolling Stones, played alongside a "Where Are They Now?" Epilogue montage: A zenith plane of Hollywood streets; Princess Carolyn and Vincent packing for their cruise through the Bahamas, each one showing the other their swimsuits and embracing; Margo Martindale in a prison not too dissimilar from Orange Is the New Black, meeting Suzanne "Crazy-Eyes" at the cafeteria; Herb not needing his IV injection and joking around with his nurse; and lastly BoJack alone late at night, rewatching Horsin' Around reruns. Then, it fades as the morning comes, and BoJack heads toward the observatory.
- "Back in '07", an alternate parody version of "Back in the '90s" that plays during the end credits, is a very hilarious, self deprecating recount of BoJack's unsuccessful return to television acting in 2007.
Fish Out of Water
- "Sea of Dreams" is a very beautiful ode to love and friendship, which plays later during Bojack's adventure in an Underwater City.
Brrap Brrap Pew Pew
- "Get Dat Fetus, Kill Dat Fetus" is a very morbidly twisted pop song by Sextina Aquafina about abortion.
That's Too Much, Man!
- "Venus, The Bringer of Peace" from Gustav Holst's The Planets fittingly and beautifully plays at the planetarium when Sarah Lynn finds her own peace.
That Went Well
- Saint Motel's "Cold Cold Man", the song playing in the Season 4 trailer, beautifully fits with the preview for this season, and there's some Fridge Brilliance in a song that talks about a man being unable to express his love being the theme for this season.
See Mister Peanutbutter Run
- This episode concludes with "I'm Mr. Peanutbutter", which is yet another catchy, alternate parody version of "Back in the '90s", but this time, it's from Mr. Peanutbutter's point-of-view, as he makes some weird promises for his political campaign in the California gubernatorial election.
The Old Sugarman Place
- Michelle Branch's and Patrick Carney's cover version of the song "A Horse With No Name" is a very fitting opener to this episode, as we check in on what BoJack has been up to since we last saw him.
- "I Will Always Think of You", a 1940s-style musical number sung by Honey Sugarman and Eddie, as they both mournfully reminisce about their respective lost loved ones (Honey's son Crackerjack, and Eddie's wife Lorraine).
Stupid Piece of Sh*t
- K. Flay's "Blood in the Cut", which plays over during Bojack's inner monologues. It's a fitting song for somebody who wants to drown out their self-loathing with anything they can get their hands on.Guess I'm contagious, it'd be safest if you ran
Fuck, that's what they all just end up doing in the end
- Tank and the Bangas' "Oh Heart", heard over the closing credits. That rinky-tink style of the piano particularly, especially for the disparity between how sad the episode is and how upbeat the song is.
What Time Is It Right Now
- Jenny Owen Youngs' "Wake Up", the final song of this season finale, which plays over during Hollyhock's and BoJack's phone call, in which she is very happy to have him in her life as a brother, and he gives his first genuine and sincere smile in the entire show. The music perfectly crowns what is, to many, the most heartwarming moment of the show thus far.Make way for the new time
Can't wait on the side lines
- "Back in the '90s" is remixed a few times this season: "The Dog Days Are Over" plays a Vietnamese dub of the song; "The Amelia Earhart Story" has a lilting acoustic guitar cover; "Free Churro" has a pipe organ funeral dirge; "Mr. Peanutbutter's Boos" has a Halloween-style cover; and "Ancient History" has a high-energy metal version.
The Light Bulb Scene
- "Los Ageless", by St. Vincent, plays at the beginning and end of the episode, foreshadowing Bojack's Sanity Slippage throughout the season, as both times it plays the scenes are identical.
- "Break My Fall", by Doc Robinson, is a cool and chill ballad sung with a guitar that matches nicely with the melancholic though lightly hopeful tone of the episode's end, with Bojack making a selfless action that goes awry, Todd breaking up with Yolanda to look for someone with whom he has more in common, and Mr. Peanutbutter entering a new relationship.
- "Don't Stop Dancing", a Broadway-style number sung by Gina that takes place in BoJack's screwed-up dreams, which blends an intense jazzy tune and tap solos with lyrics that encourage BoJack to push his horrible guilt and self-loathing further down and continue to bask in the spotlight. The increased tempo and jarring ending as BoJack wakes up adds to the anxiety.So don't stop dancing baby, don't stop spinning
Don't stop belting buddy, now we're winning
Grief consumes you but you just keep grinning
The ache becomes you and it's just beginning
Don't stop dancing, nothing's certain but the curtain