Dipper securely laced up his Velcro-soled shoes and walked out onto the "floor" of the Upside-Down House. Across the room, he spotted a girl slightly older than himself, with frost-blue hair and small, elongated glasses. Her twin ponytails were hanging toward the "ceiling" below.

"Alright, kid," Grunkle Stan's voice said in his head. "This is it. Be confident."

Dipper approached the girl and cleared his throat. "Hi, I'm Dipper. Crazy place, right?"

The girl turned and gave him a flat, annoyed expression. "It's a lame tourist trap. I'm older than you and so not your type. Also, this whole sad flirting on the road thing you're doing is only going to cause trouble. Oh, and by the way, while you've been obsessing over your failed crush on Wendy, you've completely ignored the fact that you've already started a new relationship back in Gravity Falls. You should really give Pacifica Northwest a call when you get home. You two are perfect for each other."

Dipper watched in stunned shock as the girl walked away and left the Upside-Down house, which abruptly became a Right-Side-Up House.

"...huh."

Author's Note

Yeah, this is a thing now.

I won't step on Twinkletail's toes when it comes to Sugarcoat in the MLPverse, though. I'll just do crossovers like this.