Presenting: The Autism Twins
My silly Relativity Falls designs. In all seriousness, I really love the idea of Relativity Falls to explore how Mabel and Dipper's relationship could be changed by stress and a level of estrangement.
My idea for how Dipper gets mixed up with the portal is different than it is for the Stans since I don't think there'd be as much animosity between the Mays.
TW for suicidal ideation below the cut
Like the Stans, and like in Canon, Mabel and Dipper were super close as kids and throughout high school. However, we know that Dipper couldn't wait to be an adult and Mabel was clinging onto childhood, and this is what caused the rift between the two.
Dipper, just like Ford, is scouted by a prestigious school, and has his display accidentally sabotaged by Mabel. She feels super guilty and immediately comes clean to Dipper, who tries to fix it, but can't. Whe their parents catch word of this, they immediately begin pressuring Mabel into ways of making money, despite Dipper's protests.
Mabel makes the decision to leave on her own, rather than being kicked out, and travels the country selling whatever she can. Unlike Stan, Mabel is very successful with her work, but is manipulated into giving others her money for whatever reasons.
Meanwhile, Dipper goes through college and eventually moves to Gravity Falls. I've got a number of candidates lined up as Fiddleford, mainly Pacifica, Wendy, and Candy. Regardless, Dipper discovers Gideon Gleeful, Chaos Demon (probably). Anyway, Gideon gives Dipper plentiful knowledge, and everything that goes down between Dipper, his assistant, and Gideon is the same as Ford, Fiddleford, and Bill.
Eventually, after totally isolating himself, Dipper is at his breaking point and reaches out to Mabel, who very quickly shows up. The two talk for a while, until Dipper shows her his notebooks. Dipper's behavior makes Mabel anxious, and his poor word choice convinces her that Dipper's request to her is to carry out a suicide. Mabel refuses Dipper's offer and lashes out at him. She becomes increasingly agitated and accidentally turns on the portal.
Being closer to it than Dipper, it begins dragging her to it, almost sending her through. Before it can, Dipper trades places with her, and is sucked into the portal instead.
Mabel is left alone and confused in Dipper's lab, waiting for several hour for him to come back. When he doesn't, she has a mental breakdown and reads through all of Dipper's notes and journals. Just like Stan, she devotes the next 30 years to getting her brother back while she pretends to be him.
