Lisa makes a new friend, Addy (Joey King), who shares her love of ponies. Unfortunately, Addy is peer pressured to be mean by some other girls.
- All Girls Like Ponies: Zig-zagged.
- Lisa and Addy bond over their mutual love of a book series about horses. Addy's parents happen to be horse breeders, which cements their friendship further. The mean girls, however, make fun of them for liking horses; Lisa gives Addy a toy horse, which the other girls say is for babies.
- Bart, on the other hand, hates horses, saying that boys got all the cool animals and that cars made horses obsolete anyway. Later, it's revealed when Lisa tries to escape with him on one of the horses that Bart is actually afraid of horses.
- Beware the Nice Ones: It doesn't take much to convince Lisa to try revenge or for her to pull it off.
- Big Brother Instinct: When Bart intercepts Lisa’s call to Grandpa Simpson, he’s more than content to let Lisa suffer, but when she says the girls are meaner than him, he’s off to the rescue.
- Chekhov's Gun: Addy tells Lisa that her vest can be inflated in case she falls off her horse. Later, Addy defeats the mean girls by deploying their vests.
- Closed Circle: Lisa is happy to go on a sleepover, but due to Homer and Marge taking a party cruise with spotty service and Grandpa's ineptness at home when Lisa wants to leave after being bullied she finds herself stuck there. Bart has to take a rideshare and then help her break out.
- Content Warnings: In-universe, "Thank God I'm Dead" has a bunch of them, all pertaining to how dark and disturbing the show is. They range from warning the audience that the show is "scary", "troubling" and "may cause nightmares", to mentioning that one of the censors quit the show and hasn't been seen since, and that lab mice developed anxiety just from reading the content warnings.
- Continuity Nod: Patty and Evelyn, last seen on "Livin' La Pura Vida", are seen on the cruise. Likewise, Mike Wegman from "Go Big or Go Homer" is seen boarding the cruise.
- Didn't Think This Through: After Addy's Heel–Face Turn, Lisa suggests she come with her and Bart and says there's nothing left for her here. Addy points out this is her house and is where she has all her stuff. An embarrassed Lisa says she'll instead see her at the library.
- Disowned Sibling: Frustrated by his bullying, Lisa decides to "un-brother" Bart, severing their sibling bond with a pair of safety scissors. He takes it hard, but with the parties concerned being eight and ten years old, it's perhaps unsurprising that this lasts only as long as it takes her to need his help.
- Hidden Depths: When Lisa formally severs their sibling bond, Bart is actually surprised and saddened.
- Hypocritical Heartwarming: When Lisa calls Bart for help, Bart taunts her with the fact that she "un-brothered" him earlier and he therefore owes her nothing. It's only when she tells him that the girls at the slumber party are meaner than he is that he snaps into action.
- Kids Are Cruel: The rich girls act like high school bullies.
- Living Dinosaurs: A Brachiosaurus walks by during the Shout-Out to Jurassic Park (1993).
- Lost in Transmission: Lisa tries to call Homer to take her home, but the reception at the cruise is choppy and cuts off every other line, making Homer think Lisa is okay. Lisa then tries texting, but every other text fails to upload, again making Homer think nothing is wrong.
- One-Episode Fear: Horses, for Bart. In previous episodes, he's lived comfortably with a pony in the house, idolized a cowboy, ridden horses at a dude ranch, been locked in a stable with no problems and even owned his own horse and enjoyed a brief career as a jockey.
- Outgrowing the Childish Name: The mean girls refer to Addy as Addison, which she goes along with to gain their favor. In the climax, Lisa asks to talk not to Addison the wannabe mean girl, but to Addy her friend.
- Paper-Thin Disguise: Skinner has no idea his rider is Sitcom Arch-Nemesis Bart Simpson, despite his disguise being little more than a hat and sunglasses, and barely disguising his voice at all (although the fact that it's at night may mean the darkness is contributing to Skinner's lack of observation).
- Peer Pressure Makes You Evil: Addy has joined a clique of spoiled rich girls and is going along with their mean putdowns of Lisa so they would like her better. She offers Lisa to join her and then invite an even bigger loser girl to the next party so that they can make fun of that girl.
- Plastic Bitch: Lisa is invited to the birthday party of her friend Addy. At the party, she meets Addy's other friends who are all alpha bitches. One of these friends is a girl who can't express emotions because she was exposed to botox in the womb. Addy is jealous of this, suggesting that their influence is rubbing off on her.
- Punny Name: When Bart orders an Uber, he disguises himself as "Juan Starnotip". As in he gives a one star rating and doesn't give tips.
- Revenge: Bart advocates this to Lisa rather than running away. She takes him up on it.
- Rich Bitch: Four of them, until Addy's Heel–Face Turn.
- Series Continuity Error: Bart reveals he has a fear of horses despite the fact that he was a horse jockey in a previous episode (although he may have just gained this fear after he quit the jockey business).
- Shaming the Mob: Marge and Homer accidentally ruin the party cruise by knocking off the band's set list and losing the alcohol overboard. Homer manages to calm them down by reminding everyone that they do these events to try and not feel old and remind them of their obligations at home, but feeling old and tired when they get home is inevitable anyway.
- Shout-Out:
- The title is one to The Hateful Eight.
- The shot of the horses on Addy's ranch is accompanied by the score from Jurassic Park (1993). As an added nod, a dinosaur is seen walking behind Lisa in the next shot.
- The show the girls watch ("Thank God I'm Dead") is a parody of 13 Reasons Why.
- Special Guest:
- Teachers Out of School: Principal Skinner is Bart's ride share driver.
- Traumatic Haircut: Lisa's revenge is to dip the other girls' braids in hoof hardener while they're sleeping, causing the braids to break off and leave them with spiky hair just like Lisa's.
