Crack(ish) Gravity Falls theory about: Bill Cipher and Stan's relationship

Okay.
So I know a ton will yell at me for pointing at the obvious but doing it anyway because I just realized it but whatevs.
I'd like to point out the picture Bill projected when hearing the name Stanford Pines.
The picture is an angry Stan about maul someone.
Kind of.
I know the fact that he recognizes him and agrees to do it after some thought may show that they had some sort of malice held towards each other.
Perhaps Stan is not the author, but rather had a very close relationship with him?
Think about it for a bit.
He was looking for the journals and carried on the lab.
Assuming the Stanely twin theory is correct, we might assume that the author is his twin.
This also is most likely wrong, but I'm pointing it out anyway.
Additionally, this may have been discussed in the fandom which I'm not too active in.
Including the fact that I don't have a tumblr, nor do I know any fallers there.
Anyways, just remember!
Reality is an illusion, the universe is a hologram, buy gold, bye!