(WARNING: Spoilers ahead)
Feel free to spread this theory around, but please don't take the credit- you don't have to link here, although that would be nice, but if someone asks if you came up with it... well yeah haha
This theory probably already exists, but eh... My version? O.O
So I have this theory about Gravity Falls, mainly, who wrote those books with all that info in them. (the hand with the number? Dipper has the one with 3 on it and Gideon has the one with 2 on it? I think) I think Grunkle Stan wrote them. But during book 3 (which I think is the last one, since it randomly stopped) something traumatizing happened to him, and he pretended he didn't know all that paranormal stuff happened. And then, over time, he really did forget what happened. (that can happen in real life, I think.) Another theory is that someone else, 'Him' or whatever wiped Grunkle Stan's memory because he knew too much.
Or make Grunkle Stan is
him???? Maybe Dipper is the reincarnation of Him.. Or... Something...???? Still need to think about that. So yeah, just a little one...
Oh, and you know the episode with the wax figures and stuff? Is the redhead girl supposed to be Lizzy Borden or something? Cuz, you know, the axe and all that... Or old royalty or something? xD So confuzzled