Did the Core brainwash Marcy via dark magic, advanced technology or some kind of More than Mind Control kind of means? How truly responsible is Marcy is for her villainous actions if this is the case?
Does the Core genuinely care about Marcy beyond more than making her their vessel? Or are all its Pet the Dog just manipulations to ensure her loyalty to them, despite being family? If it's the latter, then why did they decide that Marcy can be at the "helm" of the Mind Hive?
Was Marcy ordered by King Andrias to hold Sprig hostage, or did she do so on her own accord? If it was the latter, was it a cold, calculated move or a spur-of-the-moment decision born out of desperation.
Marcy The Quisling can be seen as this during the throne room fight with her Madness Makeover on display, and especially after she comes out of her coma and willingly becomes Darcy.
Same goes for the Core in both in its Mechanical Abomination and human avatar forms (especially with the latter's Game Face shown) acting as an Evil Mentor to Marcy that succeeds in its Corrupt the Cutie agenda. Its considered by many readers a more interesting Big Bad than the show, and its scene as it becomes Darcy is no less disturbing.
Cry for the Devil: Despite her being a Fallen Hero in the story, you can't help but feel sympathy for Marcy as she breaks down crying in the Core's embrace over her failure to bring her former friends to her side, as well as her emotional Parental Neglect and essentially being brainwashed into being a villain by the Big Bad for its own agenda.
This also includes the Core in this story, the Mind Hive that not only has Amphibia's past rulers and greatest placed into a Mechanical Abomination, but contains some of Marcy's direct ancestors, too. In this story, the Big Bad is given much more character expansion than in canon and it acts as a compellingly interesting Evil Mentor to its protege/descendant, Marcy.
Foe Yay Shipping: Despite claiming to see her like a sister, Marcy's feelings for Anne can be interpreted as romantic in nature of a jealous ex to the readers in a Yandere-like fashion. Even the Core brings up that her actions and borderline obsession with Anne don't appear platonic to them.
Marcy, despite pulling a Face–Heel Turn, still Hates Being Alone due to suffering Parental Neglect so much that the idea of being separated from her only friends caused her to send them to another world just so that they wouldn't have to be apart, and when they find out the full scale of her betrayal they end their friendship with her. Despite causing a lot of pain, seeing her downward spiral from the Core's manipulations is heart-breaking to read. You can’t support her actions but you can empathize with her.
Even though she's bossy and irritable, Sasha was genuinely hurt by Marcy's Face–Heel Turn. Indeed, when Anne calls her "a horrible friend" in a fit of rage, Sasha was shaken by her words and takes them to heart, resolving to become a better person and friend as atonement. Despite what she's accomplished, Sasha still doesn't know whether she’s a good leader or not, at one point wanting to give up.
Marcy's mother, Grace Wu, is also this. Despite having Took a Level in Jerkass, she's become an emotional wreck who's turned to alcoholism, believes her marriage is on its last legs due to her growing resentment towards her husband, and feels genuinely betrayed that the Boonchuys knew where her daughter was her months and didn't tell her. On top of that, she has no idea of her daughter's Face–Heel Turn and she hates her.
Love to Hate: The Core may be the reason for Marcy's Face–Heel Turn, but it's an interesting Evil Mentor with genuine fondness for its descendant, teaching her life lessons and her ancient and impressive heritage, while acting as the The Corrupter to the girl.
If Marcy willingly joining King Andrias in his plan to conquer the multiverse, starting with Earth, and attacking her friends when they refuse wasn't enough to cross it, dropping Sprig out the window after Anne calls him her best friend certainly is.
If the Core didn't cross the MEH by leading the multiverse conquest thousands of years ago, then brainwashing Marcy, a 13-year-old girl that is their direct descendant, into becoming a Fallen Heroand happily merging with them certainly does it.
Realism-Induced Horror: For many people, Marcy being corrupted by the Core is similar to being indoctrinated into a cult or extremist group, as well as the girl's unhealthy possessiveness of Anne.
Shocking Moments: Instead of King Andrias dropping Sprig out of the castle window, its Marcy!
Poor Anne. After the events of one of her best friends' betrayal from before, all she wants to do is forget and move on. She suffers hallucinations of Marcy mocking and taunting her about killing her family due to having so many sleepless nights. It's not hard to feel sorry for her.
Sprig, the poor kid is so traumatized by Marcy, someone he was supposed to trust, attempting to murder him by dropping him off the floating castle that he doesn't know who the heck he’s supposed to trust anymore.
Anne's parents, Oum and Bee, parents aren't safe from PTSD either. They had to cope with their daughter being gone for 5 months starting on her birthday, which is heart-breaking to read about with Oum who had turned to drinking and had to see a therapist after having a mental breakdown from the stress.
Marcus Wu. Despite being a strict father and not being the most understanding parent, he genuinely loves his daughter and blames himself for Marcy running away from home because he took a new job, believing it was for the good of his family, out of State forcing them to move and told her at the last second. He also has to deal with his wife's Drowning My Sorrows until she drinks herself sick and her Sanity Slippage for almost a year and finding out the Boonchuys, who he considered to be friends, knew where Marcy is and didn't tell him at all.
