Reunion Falls AU - a gravity falls au in which mabel and dipper, for (possibly supernatural) reasons unknown, were separated at birth, and while mabel grew up as an only child in her normal home with normal parents, dipper grew up in gravity falls raised by grunkle stan. but at age 12 mabel learns of dipper’s existence and decides to pay her long lost twin a surprise visit, completely unaware of the kind of wacky business going on in his hometown more on this later!!
What if in the ‘Not what he seems’ Gravity Falls episode, Mabel had to get sacrificed so that Stanley could come back home. And years later Dipper would try to bring Mabel back and they’re all aged up and Grunkle Stan, Stanley and Waddles are not there anymore because they all passed away. And either Gideon or Bill would take over Gravity Falls. What if that actually happened?! I’m such a horrible person. I’m going to hell for this.