Mystery Shack is Back is a party celebrating the grand reopening of the Mystery Shack after Gideon's defeat. The event takes place during "Scary-oke."
Stan announced the party to a small crowd of people at the Mystery Shack, including reporters Toby Determined and Shandra Jimenez. The party takes place that night outside the Mystery Shack. The area is decorated with black light posters, strings of lights, Stañatas, and a disco ball. Tables with snacks and punch are set up as well. Mabel provides a karaoke machine for party-goers and the Pines family to use. The event was interrupted by a roaming hoard of undead summoned by Dipper.