During an excavation of human artifacts, Finn, Jake and Susan are greeted by a mysterious new stranger who may hold the key to the past.
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In Beautopia, Finn, Jake, and Susan Strong break down a door during high tide that reveals an arcade. Jake doesn't seem to like the place, but Finn says that they are investigating early human culture, so they'll probably find all kind of cursed artifacts. Jake starts to get a little bit excited, since it has been a while since he has received a good hex.
While walking through the arcade, Jake states that someone could get cursed and that he hopes it's him. Susan comes across an old merry-go-round buried in sand and they pull out. Finn says he thinks that it's the bones of a prehistoric horse that was covered in feathers and used its poles to sting people who tried to steal its honey. Jake doesn't seem to believe Finn and states that he said there would be hexes. He is unable to finish his sentence when he trips over a dinosaur plush buried in some more sand.
Jake sits up and thinks that the dino plush is a "demon." He pulls it out more and sees that it is only a dino plush and refers to it as a little cutie. The ground begins to shake and Jake thinks that this is because the dino plush is cursed. Finn thinks there is an "Ooo-quake" and with that, he and Susan take Jake with them and run outside.
They come outside to see a massive animal-like robot digging its way to the surface right next to Beautopia. Finn, Jake and Susan stand outside it to see what appears to be the eye of the machine open to reveal a walkway down to where they are. The fog clears and Tiffany is standing on the walkway with a bionic arm.
Finn appears happy to see him and thought that the worm queen ate him. Tiffany then tells the gang to come with him and that he'll explain almost everything. Finn, Jake and Susan shrug to each other and follow Tiffany inside. The door opens for them and a robotic voice welcomes them. The Walkway continues and winds around a corner. There are flowers and various shapes floating and growing around them.
When walking around Susan acts suspicious, as she walks to a door she makes a strange computer sound which opens the door and Fin asks people when she learnt Robot. She then walks to a large flower object and makes the same computer sound as before causing the flower to open and a strange person in a jellyfish like suit is shown momeritng the characters, as she turns around shocked. She says she's doctor Gross and is Tiffany's boss and the one who gave him the mechanical arm, and the two decide to take Finn, Jake, and Susan a tour of the ship.
She takes them to a large room full of large and small hybrid animals, all of which have implants on there heads, as Dr Gross sings a song about evolution as the trio look around. She shows a shark mouse hybrid that can breathe air and eat chesse. A giant chicken with wasp wings, and a gigantic dragon eel hybrid that is kept in a huge tank, and there are many more. And dr Gross shows the, her favorite a bear that can tell time, which has grandfather clock for a left arm and a clock on it's tummy, we also saw this bear in the episode Hoots. Finn then asks if there's a any ordinary animals but Dr Gross says that they don't and if they did they probably died from envy.
- The time bear that appears as one of Gross's projects also appears in one of Finn's dreams in "Hoots."
- Jake also shape shifts his hand into a camera, acting as if he's taking a picture with one of the hybrids, as he did in Finn's dream although it was an actual camera.
- A Farmworld Finn hat can be seen inside the grabber claw game.
- A scientist traveling in a vessel resembling a narwhal could be a reference to Jules Verne.
- Doctor Gross's song, "Evolution" sounds similar to Gene Wilder's "Pure Imagination" from the 1971 movie, Willy Wonka and the Chocolate Factory.
- The dino plush discovered in the arcade is one of the monsters from the Sea of Monsters in the Beatles' movie Yellow Submarine.
- The structure of the giant drill station look similar to Drimogemon.
- The time when the creatures escape look similar to the scene of the release of the monsters in the film The Cabin in the Woods (2011).
- Susan's escape looks similar to the final part of videogame "Metroid Fusion", where Samus while fighting the SA-X, she tries to escape from the BSL Station on the planet SR388 by releasing several species that were trapped inside a laboratory.
- Tiffany survived the supposed death he endured in "Dentist" which resulted in losing his arm.
- Dr. Gross makes mention of an island full of human inhabitants, something that the eighth season's "Islands" miniseries will expand upon.
- The paralyzing juice has a similar effect to the paralyzing potion in "Still."
- This episode along with "Reboot" are the finale for the seventh season. They aired on a Saturday at a new time slot (8:00 PM).
- This episode along with "Reboot" aired in Turkey on October 25, in South Africa on October 26, and in Italy on November 16, 2016 before its intended U.S. airdate. 
- With 0.77 million viewers (approximately 770,000 viewers) on its premiere, "Preboot" and "Reboot" are some of the lowest watched episodes of Adventure Time (now surpassed by "Horse and Ball"), most likely due to the episode getting no promotion, and a last minute time change.
- While Dr. Gross sings the song "Evolution," Tiffany is seen with the gang, but as they enter in the menagerie, he disappears.
This episode was censored in some countries. See Censorship of Adventure Time for more information.