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.
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 cursed artifacts. Jake starts to get a little bit excited, since it has been a while since he has received a 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 then pulls it 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 to see what appears to be the eye of the machine open to reveal a walkway that extends down to where they are. The fog clears and Tiffany introduces himself 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 Finn asks when she learned Robot. She then walks to a large flower object and makes the same computer sound as before, causing the flower to open, revealing a strange person in a jellyfish like suit. She is shown monitoring the characters, then turnings around shocked when she realizes they see her. She says she's Dr. Gross and is Tiffany's boss and the one who gave him the mechanical. 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 their heads. Dr Gross begins to sing a song about evolution as the trio look around. She shows a shark mouse hybrid that can breathe air and eat cheese. A giant chicken with wasp wings, and a gigantic dragon eel hybrid that is kept in a huge tank, and there are many more. Dr. Gross shares her favorite hybrid,a bear that can tell time, which has a grandfather clock for a left arm and a clock on it's tummy. Finn then asks if there's a any ordinary animals, to which Dr Gross replies that they don't, and jokingly says if they did they'd probably die from envy. A skorp-munk tapping on glass catches Jake's attention, and it then proceeds to dance hoping to warn Jake. After Jake feels that he is being warned, Dr. Gross hastily recommends that they move on to look at other things.
Dr. Gross leads the group to her "Examination Room," which Jake repeats to Susan. Dr. Gross then brings up seats and lollipops for her guests on account of their good behavior. Susan is reluctant to accept her lollipop, however Finn and Jake eat theirs without hesitation. Dr. Gross then takes off her suit, revealing that she is human, albeit cybernetically enhanced. Dr. Gross then goes on to explain that modifications are not only beneficial, but logical. Her intentions for bringing them become clear as she explains they are being hired, and their interrupted loyalty will earn them upgrades. After Jake tries to use his stretchy powers, Finn and Jake learn that they have been paralyzed from the lollipops, and Susan shares that she cannot move either. Dr. Gross calls up her assistants to help her begin prepping the group. Dr. Gross reveals her agenda to make all humans cybernetically enhanced, implying that more humans still exist. When Dr. Gross begins prepping Susan, she notices Susan already has an implant, however the implant is one from someone else. It is also revealed that Susan never ate her lollipop dosed with paralyzing potion, which allows Susan to fight her way out of the Examination Room and take Finn and Jake with her.
Dr. Gross signals her hybrid animals, causing them to transform into a cybernetically enhanced version of themselves. The hybrid animals are then ordered to fetch up the escaping trio. The scene goes to Susan who somehow subconsciously knows the quickest path to exit the ship, much to Finn's awe. The hybrid animals catch up to Susan and try to take her down, but are easily dealt with. While Susan fights off the hybrids successfully, Tiffany fires a net that finally subdues them. Dr. Gross attempts to use a buzz saw to cut up the helpless trio, but she is betrayed by Tiffany, knocking the saw out of harms way. Susan busts out of the net, and fires a net taking down Dr. Gross. Due to the damage to the ship from Dr. Gross's saw, the ship begins to self-destruct. Still holding onto Finn and Jake, Susan leaps out of the ship in time before it submerges and explodes.
Now outside, Finn and Jake look at the freed hybrid animals. The episode ends with Finn's worries coming true, due to the "giant electro-eel" escaping and heading to the Candy Kingdom.
- A Farmworld Finn hat can be seen inside the grabber claw game.
- The paralyzing juice has a similar effect to the paralyzing potion in "Still."
- This is the only time in the seventh season where Martin Mertens is mentioned, not counting the episode Don't Look, in which he is symbolized.
- 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.
- Finn mentions that "bionic arms are cool" in this episode. In the next episode, he loses his grass arm, which is replaced by a bionic arm afterwards.
- The time bear that appears as one of Gross's projects also appeared in one of Finn's dreams in "Hoots."
- Dr. Gross makes mention of an island full of human inhabitants, something that the eighth season's "Islands" miniseries expands upon.
- 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, this episode and "Reboot" are some of the lowest watched episodes of Adventure Time, 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.