Arrival in Gravity Falls. Sometime during the month of June, Dipper and his twin sister Mabel were sent from Piedmont, California to the small town of Gravity Falls, Oregon, to stay with their Great Uncle Grunkle Stan, who runs a tourist trap named the Mystery Shack which doubles as his house.ipper and his friends trick-or-treating. Dipper and Mabel, like the rest of the town, are ecstatic about celebrating Gravity Falls' summer version of Halloween, Summerween, and plans to trick-or-treat with his sister, Candy, and Grenda.