The episode starts with a flashback after Marcy (who recently arrived to Newtopia using the Calamity Box and broke her left leg falling down a flight of stairs) first came to Amphibia. She is with Lady Olivia on the Newtopia Castle's balcony as Olivia shows the young human a magnificent view while she explains how her ancestors have cared for the land for generations; Marcy, who is grateful to the Newts for taking her in and helping her, promises to do her part and help them however she can. In the present, Olivia at the same balcony watches with sorrow as the Frobots with the mining equipment are plundering the capital's surrounding resources and creating lots of pollution through rapid industrialization turning the area into a bleak wasteland. Just then, a standard class Frobot arrives and informs Olivia that she has been summoned by King Andrias. Olivia meets with General Yunan, and as they peek into the king's chambers, he appears to be talking to himself. He is reluctant to go through with a certain plan but relents.
Andrias then greets the two of them in and gives them new assignments; Olivia will oversee the construction of some refineries as he plans to drain all of Amphibia of its resources while Yunan will round up any frogs she finds and force them to work in factories.
Olivia & Yunan talk about the rebellion.
Afterwards, Olivia expresses that she has had enough of Andrias' tyranny, and Yunan agrees that he has taken things way too far and tells her they need to fight back. Olivia decides to rescue Marcy to help them. Yunan is reluctant because she sees the humans as "scheming backstabbers" (likely referencing Sasha's failed coup and Marcy's deception), but comes around when Olivia points out Marcy was the only one to defeat the king at Flipwart, so she is possibly the only one who can out-think him.
After making their way to the lower chambers while evading the Frobots, the duo encounter a chained-up Moss Man and some Shadowfish roaming in the hallways; Olivia deduces that this was where the newts' ancestors kept their otherworldly prisoners.
The Core corners the trio.
Olivia and Yunan break Marcy out of her healing chamber, but just as they are about to make their getaway, the room projects holograms of their worst fears; for Olivia, her late mother appears, disappointed in her for not protecting Amphibia's environment. She transforms into a pollution monster to scare Olivia. For Yunan, a horde of evil looking Grubhogs are projected, because one nearly bit her right arm off as a kid. For Marcy, a nightmare appears of her inside an SJMS hallway. Anne and Sasha reminding her about how she betrayed them, and then morphing together into a 2-headed giant monster telling Marcy they don't want anything to do with her anymore. Yunan then discovers that there are electronic eyes covering the entire room, making the illusions. The trio teams up to destroy them all.
Yunan, Olivia, and Marcy celebrating.
After celebrating their short-lived victory, the trio try to escape again but they are stopped by Andrias' right hand pushing them back into the room who saw the whole thing thanks to a eye hidden inside his crown like a surveillance camera. Just then, a mechanical multi-eyed monster with robotic tentacles appears before them and grabs Marcy, strapping her into a chair.
Marcy screams as she is possessed (audio excerpt from "All In").
Marcy possessed by the Core.
Andrias explains that the creature is called The Core and that it is the combined intellect of Amphibia's 'greatest minds'. Andrias further explains that studying the Moss Man expanded their medical knowledge and studying the Shadowfish allowed them to cheat death, thus creating the entity. The Core now desired a host which has to be the smartest, so it chose Marcy because as previously stated by Olivia, Marcy was the only one to defeat Andrias at Flipwart. Andrias admits he always liked Marcy but his master had chosen her and he had no control over it. Marcy struggles, but it's pointless as a helmet is placed on her head. Olivia and Yunan watch in horror as Marcy screams in agony while the Core downloads its consciousness into her. The Core, now one with Marcy, forebodingly greets everyone as the screen fades to black, with only the eyes of the Core showing on screen.
This is the second end credits sequence (following that of "Little Frogtown"/"Hopping Mall" and followed by that of "All In") to not show any characters.
In the Hebrew, Polish and Thai dubs, the audio of the standard Season 3 credits sequence (i.e. Anne's Theme) is nevertheless reused.
End credits ambience (sped-up)
Some have theorized that screams (presumably those of Marcy) could be heard when the credits are sped up. When asked about it on Twitter, Matt Braly responded that this was coincidental.[4]
This is the fourth of five episodes in the entire series to not feature any of the main 4 characters. Although, they are mentioned, and Anne and Sasha appear in a vision of Marcy.
The Frobot in this episode is voiced by Matt Braly instead of Troy Baker like in other episodes.
The word on Marcy's rejuvenation tank translates to "host" in the Amphibian alphabet.
Haley Tju is credited for voicing both Marcy and "Darcy," the latter presumably the name of the Core-possessed Marcy.
The name of the Core-possessed Marcy was confirmed to indeed be "Darcy" during the episode "The Core & The King" which it gives to itself in said episode.
This is the only episode to use this design of the Core-possessed Marcy's eyes (although it's shown in the opening sequence), as her face is not shown in "Froggy Little Christmas".
This is the fourth of five episodes to be named after two characters in the show, the first being "Wally and Anne", the second being "Maddie & Marcy", the third being "Bessie & MicroAngelo" and the fifth being "The Core & The King".
This is the only episode featuring the Core to not use an alternate opening sequence.
Revelations and significant events
Lady Olivia is the descendant of a line of Newts who may a sacred vow to watch, cared, and protect the land of Amphibia and she inherited her role from her mother.
It has been weeks since the events of "True Colors", as Newtopia's outside area and its surroundings has become a polluted wasteland by reckless industrialization and material harvesting.
Yunan is still upset with Marcy because her betrayal but forgives her when saving her.
After Olivia and Yunan free Marcy from the rejuvenation tank, Marcy asks if they are Anne and Sasha, revealing that Marcy thought her friends would be rescuing her.
The Moss Men and Shadowfish in the basement of the Newtopia Castle are other worldly creatures that were used for scientific research because of their special abilities: the Moss Men for medical research and the shadowfish to "conquer death."
The entity that King Andrias serves as his lord is referred to as "the Core."
The fears of Olivia, Yunan and Marcy are shown through the projection holograms:
Olivia's fear is her mother being disappointed in her for failing to protect Amphibia's environment.
Yunan's fear are grubhogs because one almost bit her arm off when she was at her school.
Marcy's fear is Anne and Sasha rejecting her for her betrayal.
Upon closer inspection, the Saint James Middle School crest on the Anne/Sasha monster is heart-shaped, possibly implying that Marcy also fears that Anne and Sasha might be romantically involved with each other.
Even though he used, mocked and almost killed her back in "True Colors", King Andrias honestly admits he always did like Marcy and even tried to get the Core to reconsider its choice of host, but had to obey. He even sports some sort of look of regret or guilt as he looks away when the Core begins possessing her.
At the end of the episode, the Core has transferred its mind into Marcy's body, possessing her.
Continuity
The flashback at the beginning takes place after Marcy arrived in Newtopia with her broken left leg referencing the Marcy Theme Song Takeover, taking place after Marcy left the hospital.
General Yunan attempts to recite her monologue from her debut episode before she sees a grubhog.
This is the second episode to tease it, following "True Colors".
Marcy's illusion involves the memory of Anne and Sasha reprimanding her for her selfishness and deception during "True Colors".
Marcy beating King Andrias at Flipwart is mentioned again, after being first brought up in "The First Temple".
Andrias mentions that he always liked that Marcy and tried to protect her from the Core. A flashback to their first meeting in "All In" reveals that he was being honest.
Due to Anne not appearing physically, this episode's events are not chronicled in Marcy's Journal: A Guide to Amphibia. In its place (entry 103), Anne reflects on Marcy, feeling very hurt by her dishonesty and recounting when they first met. She also vows to make things right with her.
Allusions
Star Wars: Episode III – Revenge of the Sith - Marcy's transformation into the Core is likely a reference to Anakin Skywalker's transformation into Darth Vader at the end of Revenge of the Sith. Additionally, both Marcy and Anakin had sustained a severe burn-related injury before their transformation and were both manipulated by the main antagonist to turn to their side. However, the differences between them are that Marcy appears to be completely healed after the incident, while Anakin lost his arms, legs, several inner organs and sustained severe burns that did not fully heal.
When Marcy awakens after being possessed by the core she says why "hello there" a line spoken by Obi-Wan Kenobi in the film.
Twice - When Marcy is in her illusion, a prom promotion says Prom "Yes or Yes", a possible reference to this South Korean girl group's album Yes or Yes.
Marvel - The Core is similar to the Kree Supreme Intelligence from Marvel. As they are both entities that are a combination of their world's greatest minds.
Errors
In one scene where Andrias points at Olivia and Yunan, he has five fingers as opposed to four.
In the Anne/Sasha monster, the beauty mark is missing from Sasha's head.
Memorable quotes
“
Lady Olivia, you newts took me in when I landed here, (she sees her cast) fixed me up, (takes her hands), cared for me. I promise to do my best (with a cute face) and look after this place as well!
”
—Marcy
“
It's finally time for the core to lead us to our destiny. But what destiny you ask? Well, I suppose I should just let it speak for itself
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