Something that intrigues me about Bill’s involvement with the present Pines family is that he never bothered going into Mabel’s mind as far as we can tell. Technically, he’s never interacted with Stan despite being in his mindscape at one point, either.
He mostly messed up Ford, and then Dipper… I think in his AMA or somewhere, he said he liked being in the minds of the gullible; and when I think about it, that makes sense.
To Bill, interacting with Mabel and Stan without a disguise would prove risky in comparison to messing with Ford and Dipper. Ford was gullible to Bill’s words as long as he was falling for the flattery and other manipulative tactics strung together by Bill. He tried similar tactics of intellectual flattery on Dipper, but to no avail. So he resorted to using Dipper’s desperation for answers to Gravity Falls, as well as his insecurities about how Mabel treats or thinks of him. THIS worked.
However, Mabel and Stan aren’t necessarily gullible by Bill’s standards. Stan’s got his conman skills, and it’s possible he would smell a scam or figure out between-the-line context of contracts if he meets/interacts with Bill. Mabel doesn’t trust Bill at all, no matter how desperate she is, and she is VERY aggressive toward him. The only reason Bill managed to trick her for the Rift was ‘cause he took advantage of her not knowing of its hazards or what it is, let alone the fact he’s after it. He also took advantage of someone Mabel trusts, by possessing Blendin and trying to make a “time deal” kind of thing.
Heck, the first time Bill disguised as someone Mabel trusts, she fell for it too. When he was Soos in Dreamscaperers, he fooled Mabel then. Surely, this was a way he could tap into her gullible side without actually interacting with her in her mind and stuff.
Though… That does still raise questions. Just when I think I’ve figured out why he’s messed with Ford and Dipper more - which has always made sense as he’s a being priding himself with all the knowledge he has and those two WANT that knowledge - there continue to be questions on this matter.
In the mindscape (and peoples’ dreams), Bill could manipulate the mental environment including himself. He could shapeshift like he did in Stan’s mind, he could give nightmares and push the people into some sort of insanity if he messes with them enough. Dipper describes letting Bill into your mind as a way “he’ll wreck the place.”
So what keeps Mabel and Stan safe from this? Well, Stan of course still has the conman know-how thing, and he kinda seems to know how the mindscape works? (I’m still wondering if that was really him knowing that, or something orchestrated by Bill, but that’s another topic in itself…) But even with that, after waking up Stan claims to only recollect the “brightly colored men” in his dreams. Was he unaware of Bill’s presence, or has he chosen to ignore and avoid it?
Then there’s Mabel, and the possibility that she IS more powerful than Bill and therefore a threat to him. Is he outright unable to enter her mind? Or would he love it because he loves her “fun” as his love for chaos? Why wouldn’t he mess with Mabel’s mind?
Is Mabel like… Mentally immune to Bill? Perhaps Mabel has “It’s A Small World” stuck in her head (that Alex gave as Bill-repellent advice). That’s… Actually plausible, ahaha.
Maybe even for Bill, Mabel’s imagination is too chaotic for him to bother with or too much for him to try to “control” in the mindscape. Except that in Stan’s mindscape, despite the mildly crazy stuff going on, he cleared everything into a blank before leaving. So I’m not too sure what his limits are, and how much of the mental environment he can indeed manipulate.
But if Bill were able to enter Mabel’s mind, knowing that she wouldn’t trust him in his default form, why wouldn’t he take advantage of the shapeshifting? Blend in with the strange products of whatever may be in Mabel’s dreams?
Is it possible he HAS messed with her mind off-screen, and in very subtle ways, though? Mabel has nightmares too like anyone else. I wouldn’t be surprised if Bill’s appeared in those moments to further orchestrate these nightmares “behind curtains” without her knowing, and mess with her fears at least. Messing with and inflating her fears that drove her to giving him the rift… Well, that would make sense, wouldn’t it?
I dunno, trying to figure this out probably doesn’t matter. It’s still interesting to me, though. This is the train of thought I go on when I’m struggling to sleep again tonight.