So in Dipper’s Guide to the Unexplained we all thought Grunkle Stan was just lying through his teeth (as he tends to do… or given how honest he turns out to be to family when looking closer, does he?) when he said he didn’t have a tattoo.
He doesn’t. It’s a burn.
Bonus: think about the placement of Dipper’s Goober mark that Stan drew when saying “but you do”. He obviously thinks that Dipper’s birthmark is an anomaly, just like his brother’s, and his bitter attitude towards the whole incident explains why he was so closed and petty when Dipper tried to peek.
Also, it hints to his whole attitude towards Dipper. He sees a bright, bullied young kid who for all sense and purpose is following in Stanford’s path. He’s obviously uncomfortable with Dipper at first, making fun of him and not being understood, unlike Mabel who has so many incredibly sweet moments with Grunkle Stan in Season 1. But Stan’s not giving up on his family after fighting and abandoning them hurt so much. So he tries to have his influence on the kid, teach him to fight, to stand on his own, to value his sister and basks in the sheer enjoyment of watching the two love each other. He’s worked so long to save Ford that he doesn’t imagine waiting now that he has the journals, so he keeps plowing ahead, but he’s hoping that his care and his redemption can shape the kids to be better than them, to support each other.
And that’s why he’s so scared of Ford being around the kids. He knows Dipper’s obsessed, he knows Ford’s happy to see them, and is so out of touch that he’ll drag them in (he didn’t know how to interact with people, or when it would’ve been so much better for Fiddleford to have been left out of it). But more than that all Stan knows of Ford is how he used to be, how he was when they fell apart, because the one time they reunited he was clearly under paranormal influence and was worse.
Hearing just one side of the story means that the twins will stick together, will want to stay close and stay away from whatever dangers are obviously going on here. For all Stan knows, bringing Ford’s side in might tempt Dipper to keep digging deeper, and either leave Mabel behind or get her hurt.
But Ford didn’t tell his side of the story. Not even Stanley knows it. And those secrets - what Fiddleford saw and what happened after he left - is going to get everyone involved again.
"Literally I've been following him around for weeks...
and I've never once seen the right side of his face...
and neither has anyone else. But why?
DAY 5, Entry #2 "TOOTH"
"I don't know, I've been looking for... there it is.
Okay, after it attacked us, that giant head thing just
sunk back into the lake, and it lost another one of its teeth
trying to eat our boat! But the important thing is, we survived.
DAY 5, Entry #3 "THE HIDE-BEHIND"
"Hide Behind? Oh, he's real alright. Real as my beard!
He was behind me once; made this sound: tchktchktchktchktchktchk.
"Oh, the Hide Behind is definitely real.
He might even be behind me right now! Let me see..."
"Don't believe every legend you hear, kid. The people in this town
are literally the dumbest people in the world.