Fun in Vegas

Dipper and Mabel Pines have finally turned eighteen and their parents have taken them all the way to fabulous Las Vegas for a weekend of fun as their big gift to them. Mabel is right at home in the flashy city, but Dipper finds it to be a bit of a headache, and searches for some quiet. Instead, he finds the most exciting 'person' he has ever met. This is a Dipper/Bill Cipher fic.