We all think of Bill as a demon but is he really? Does he actually need to keep true to his word?
Gideon is the one that calls him a demon–Gideon calls a lot of people demons btw I’m pretty sure Bill freaked the kid out on purpose–because he has to summon him, but Bill doesn’t appear in Gravity Falls he appears in the mindscape. He is, in a loose sense of the word, an alien. While he isprojecting his image “into our minds” as Ford says, what’s not to say this just isn’t some technology?
Bill says he’s the master of the mind and yet needs Mabel and Soos to find the code to the safe in Stan’s mind?
He needs Ford to make a portal–a very scientific object–in order for the rift to open. Not magic.
What is it? “Magic is just science we can’t explain yet”?
This fandom all hangs onto the deals. That Bill has to stick to them, but Alex said a while ago that he doesn’t. That he’s not caged in this idea of a “deal’s a deal”. He makes them just like we make them, but just like us, he can break them at any time.
He crushed the laptop not on some weird “give them a clue” sort of thing, but because he didn’t want Dipper to find out what was on it.
We know nothing about Bill Cipher except that he can enter the mindscape, comes from another dimension, and is a total frat boy. He never claims he is a demon, he just let’s people believe it.