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Mabel Pines was in tears when Blendin Blandin approached her with an offer. But she knew something about him that he didn’t want her to.
“Bill Cipher!” She cried. “Just who I wanted to see!”
“Wh-what? No, it’s-it’s me, Blendin Blandin!” He replied. “Wait, what did you say?”
She reached inside her backpack and pulled out what appeared to be a snowglobe. “Here, take the Rift, which I definitely know exactly what it is. I want to betray everyone, join the guy who tried to kill my brother and frame it as a suicide, and be trapped in a land of emotional manipulation!”
“All right then, Shooting Star,” Bill-as-Blendin agreed. He stomped on the Rift and put Mabel in a bubble made up of things from her childhood where her every desire would come to fruition. This has been shown to have zero adverse reactions at all. Mabeland even made her a new brother who was nothing like the old one, because she wanted her brother but the real one always managed to pull her back into reality. So this was a Mabelized version of him. Or was it a Billized version of him? We don’t know who made Dippy Fresh, after all. Anyway.
Three days later for Dipper and one week later for Mabel, Dipper, Wendy, and Soos enter Mabeland. Stuff happens and they end up having a trial.
“Mabel,” Dipper said, “I know you want me to stay with you. But at twelve years old, I know exactly what I want for the rest of my life and that is to be apart from you studying under Great Uncle Ford, which is a completely healthy life for a teenager. I have put a lot of thought into this and after riding the high of an adventure, this is where I belong. In the basement. And in the forest. But mostly in the basement, since that’s where Great Uncle Ford spends all his time. You must go and do high school without me, because siblings should be separated when they’re teenagers and never reconcile.”
“But Dipper!”
“No, Mabel.”
Mabel burst into tears. “I’m a traitor! I betrayed you all by giving the Rift to Bill and I knew exactly what I was doing! Mwahahahaha!” Her evil laugh echoed throughout all of Mabeland and out into Gravity Falls.
Her Grunkle Stan, who was at the Mystery Shack, looked up and said, “I taught you how to be a crook, but I never wanted you to be a supervillain. This isn’t you, pumpkin.” Unfortunately, Mabel could not hear him from her bubble.
Dipper looked at her with disbelieving eyes. “First you hold me back from my destiny, then you betray me? We should never speak again!”
“Dudes, I’m sure there’s a perfectly reasonable explanation for all this–” Soos said.
“She made a new me! She doesn’t need me, just some fake!” Dipper retorted.
“I’m sorry, Dipper. I just love my land of emotional manipulation so much that I could never leave it behind, not without you,” Mabel said.
“But you’re the Mystery Twins,” Wendy said. “You’re practically unstoppable together. You’re each other’s support system, greatest cheerleader, shoulder to cry on, friend to make fun of . . . you need each other. Even if you go your separate ways after you graduate–”
“I’m on Bill Cipher’s team, Wendy. I’m sorry,” Mabel said.
“How’d you even know what the Rift was anyway?” Dipper asked. “Great Uncle Ford specifically told me not to tell anyone about the super dangerous snow globe that would cause the apocalypse if it broke.”
“The Power of Mabel, but evil!”
“That’s not a thing, Mabel.”
“It is now!”
“So do you want to be on Bill’s side, or do you want me to do life with you? C’mon, Mabel, pick one!”
Mabel looked around at her much-too-brightly colored bubble. She faltered. “I . . . I don’t know.”
“That triangle guy is bad news, Hambone,” Soos said sympathetically. “Why don’t you come out with us?”
“But Dipper is going to leave me behind,” she said sadly. “How am I supposed to go through high school without him? I’ll probably find out that all my crushes are just gnomes in trench coats again!”
“Oh, Mabel, I guess I’ll give up my dream to be with you. I’ll just have to learn from Great Uncle Ford in the summertime. This is a huge sacrifice, because our parents would definitely let me live apart from them with an uncle they barely know year-round for the rest of my teenage years,” Dipper said, sighing.
“Thank you so much, but I’m still on Bill’s side,” Mabel said. “Now come here for a sincere sibling hug!”
They hugged, the world crumbled, and they ran. “Glad you came with us, Mabel,” Wendy said.
“The Mystery Twins wouldn’t be the same if they were split up,” Soos added.
“Thank you, but I’ve realized . . . Dipper, if you want, you can stay. I won’t hold you back,” Mabel said.
Dipper gave her a strange look. “But I want to stay with you. You’re my sister, and we need each other.”
“But you just said–”
“I changed my mind. You’ve always been there for me, like I’ve always been there for you. I can’t just leave that behind and pretend it doesn’t matter. Siblings are special.”
Tears dripped down Mabel’s face. “Thank you. You know, I didn’t actually know what the Rift did. I thought it would give me a little more summer. It wasn’t good of me to take that deal, but I was hurting and didn’t have all the facts. I just wanted . . . you.”
“I’ll stay by your side,” Dipper promised. “I knew you’d never willingly hand the Rift over to Bill after what he’s done. Not if you knew what it was, or if you knew who it was you were really giving it to. Part of me is upset, but I forgive you.”
Soos sniffled. “It’s just . . . so beautiful, dudes.”
“Mystery Twins reunited!” Wendy exclaimed, pumping her fist into the air. “Now let’s get back to the Shack. We can regroup there and figure out what to do next.”
They nodded and set off.