Board Thread:General Discussion/@comment-12265996-20141202030018/@comment-25020257-20141220225417

Captainkirk wrote: 1. Stanley Pines (Stanford's alleged brother)

2. Bill Cipher

3. Quentin Trembly

4. Future Dipper (I put no stock in this theory, but were including ALL possibilties)

5. For all we know the author left Gravity Falls and lost it. If your Including All posibillities it could be Stan.