When returning to Gravity Falls for the second time, Dipper creates a portal from their universe, to the universe of Steven Universe. T for possible StevenxMabel. Also, Dipper, Mabel, and Steven are all 13.
Crossover - Gravity Falls & Steven Universe - Rated: T - English - Mystery/Adventure - Chapters: 5 - Words: 1,258 - Reviews: 10 - Favs: 7 - Follows: 9 - Published: 8/8/2015 - Dipper P., Mabel P., Steven U., Peridot