(Inside the Mystery Shack)

Ford screamed at the top of his lungs and walked back and forth as his brother, the twins, Soos and Wendy went to check on him. "I can't believe I overlooked such an important detail!"

"What is it Grunkle Ford?" Dipper asked.

"Because the unicorn hair only protects the shack from the inside, anybody who's outside the shack can still be possessed by Bill!"

Everybody gasped, except for Stan, who raised an eyebrow in confusion, and Wendy, who uttered "So much for beating up an unicorn."

"What do we do now?!" Mabel exclaimed.

"Nobody worry," Ford uttered before adjusting his glasses and dramatically adding, "I have an idea."

(Some hours later)

The Mystery Shack was filled to the brim with all the residents of Gravity Falls, with Ford, his brother, the twins and Wendy and Soos stuck in the middle. "In retrospective, this was a really stupid idea." Ford stated.

"And yet you didn't notice until now?" Stan added.

(Meanwhile, with Bill)

The dream demon watched the current state of the shack from his crystal ball, which angered him to no end. "To whoever thought this up, kudos to them."