When Flame Princess is coaxed into a high stakes battle against the indomitable Son of Rap Bear, Finn must help her search for a new strategy.
Finn and Flame Princess socialize and rap together at a "Clam Rap" Party. Toronto (disguised with a fake mustache as "Victor Marilyn" and claiming to be a talent scout) approaches Flame Princess, impressed by her rapping, and offers to book her for a big-time rap battle called Rap Fest-aide. He asks Phoebe to sign some waivers, which she does so with no hesitation. Toronto's fake mustache then falls off, revealing his identity. Toronto then reveals the contract FP signed says that if she loses the rap battle, he will gain ownership of the Fire Kingdom and reveals that she will face Son of Rap Bear.
Wondering who Son of Rap Bear is, Finn and Phoebe go visit Rap Bear. Finn notices Rap Bear's poor condition, and Rap Bear reveals that he was beaten by his son in a rap battle. Upon telling Rap Bear that FP would be facing his son, he said he'd take her apart and reveals to not have legs because his son had "rapped his legs off."
Finn and FP go to the Candy Tavern to watch Son of Rap Bear perform. During the rap battle, Son of Rap Bear literally tears his opponent into pieces. Son of Rap Bear then raps to Flame Princess about how she'll never defeat him, and that she has no experience or anything to rap about, literally breaking the furniture and walls with his rapping.
Phoebe realizes that Son of Rap Bear was right and that she needs life experience to rap about. FP then suggests that she and Finn go on adventures to have life experience to rap about. FP then raps in montage throughout her adventures. Despite her new life experience, Phoebe still doesn't believe she could defeat Son of Rap Bear. BMO then went on to comment on Neptr's "family," giving Phoebe an idea.
Flame Princess goes to visit her father in his new cave home among the chipmunks. FP proposes to her father about putting their past behind them and being "normal" with each other. Flame King then forgives his daughter for placing him in the lantern, though he doesn't apologize for putting her in the lantern. FP then leaves in anger.
Rap Fest-aide begins with Toronto as an announcer introducing Flame Princess and Son of Rap Bear. Son of Rap Bear begins to rap, particularly about Flame Princess and broke parts of the stadium in the process. Flame Princess proceeds to rap, though not very well, running out of rhymes quickly. FP then sees Flame King the audience, but he says he had no idea that she'd be there and that she in no way could defeat Son of Rap Bear. Enraged, Phoebe speaks in rhymes about how her father never cared for her and that she wondered why she believed the two could ever get along. FP then raps, ripping on Son of Rap Bear, impressing the audience, scaring Toronto and presumably defeating Son of Rap Bear. The crowd then runs up to Flame Princess cheering her on and declaring her the winner. Son of Rap Bear then raps to himself about how he lost and his legs fall off. Flame King then congratulates his daughter saying she's not bad.
- Jake (non-speaking)
- Rap Bear
- Marceline (cameo)
- Bun Bun (cameo)
- Kim Kil Whan (cameo)
- Starchy (cameo)
- Blank-Eyed Girl (cameo)
- Banana Man (cameo)
- Wyatt (cameo)
- Elder Plops (cameo)
- Flambo (cameo)
- Pizza Fish (cameo)
- Alarm Clock Creature (cameo)
- Candy People
- Clams and Raps
- Candy Kingdom Open Mic Rap Battle
- Flame Princess Experience Rap
- Chipmunks Rap
- Rap Fest Day Rap Battle
- The rapping chipmunk that performs for Flame King is voiced by Open Mike Eagle, who also happens to be the co-host for an Adventure Time podcast called Conversation Parade.
- Cinnamon Bun doesn't have his Flame Shield in the beginning of the episode, like in the episode "The Mountain."
- The contract that Toronto tricks Flame Princess into signing is unenforceable under the Fire Kingdom's jurisdiction, and can be argued to be in violation of multiple Fire Kingdom laws, including the Honesty Law established in Earth & Water. Whether or not the Flame Princess won the rap battle is therefore inconsequential.
- Toronto is likely a fugitive of the Fire Kingdom as a result of this episode.
- When Flame Princess sings "climb a rock," she appears to be actually climbing an insect husk, which is very similar to the shells of Ohmu from the manga and film Nausicaä of the Valley of the Wind.
- Rap Bear lives inside the monster from "Belly of the Beast."
- Flame King and Bun Bun still live in their chipmunk cave from "Bun Bun."
- Crab Princess makes an appearance for the first time since "Breezy."
- Dr. Dextrose makes a cameo appearance in this episode. He has not been seen since the season 2 episode "The Real You."
- A blank-eyed girl from the episode of the same name makes a cameo appearance.
- In this episode, FP is rocking the hat from her duo with MC Neptr from "The Music Hole."
- At the beginning of the montage with Flame Princess' rap, Finn appears with both arms.
- Flame Princess is consistently drawn as several inches taller than Finn, when prior episodes established that they were roughly the same height.