Luna-is-lost

So, first of all, you’ll need some context for all this.

This book here? I’ve seen most people assume it’s Sans’s quantum physics book due to his implied history in the science field, which makes sense, but it’s actually not—

There’s an empty space for it in Papyrus’s bookshelf :)! And we already know he has a tendency to keep textbooks/informational books due to the favorite book conversation in which he mentions “Advanced Puzzling Construction for Critical Minds”.

Anyway, he seems to be a bit of an engineer, a real hands on making stuff crafty kind of guy. He makes all his puzzles, traps, stations, heck he painted a whole rock formation to look like a bridge, and he knows Alphys on the Undernet well enough for her to send him prototype builds of things she’s made to test (the multicolor tile puzzle that looks curiously Mettaton shaped was from her).

So, what does this matter? What of it? Well. Ya know that machine in the back of the brothers’ house?

Yeah that one. I think he’s building it.

I mean, they have this machine in the back room of their house and so far only one brother is being described as busy in a shifty way. Sans has never been demonstrated as the builder inventor type (unless you count him helping to make Papyrus’s battle body outfit, which stacked up against several giant puzzles and the prototype build from Alphys is not much and actually more evidence towards him being a helper here and not the main creator) of the two despite his connections and in Deltarune he’s got a job and a social life he’s typically dealing with. If one of them was the one to be doing most of the building it would probably be The Guy We Know Is A Builder™️, ya know Occam’s razor and all.

There is the tweet that says:

Implying both were involved in the project here, but, still, Papyrus has a lot more free time for that, so I’d have to imagine logically he’s the one doing most of the work on it and that Sans probably helps out whenever he’s at home (much like the battle body situation mentioned earlier).

But this begs the question: Then why is the key to that lab in Sans’s room?

Easy!

Sans is the one who still cares about it. Papyrus? Not so much.

We don’t see Papyrus lamenting about not being able to “go back” (whatever that entails). He barely mentions or acknowledges any of it. In fact, he totally avoids saying much about where he lived before Snowdin.

I’ve seen a lot of people take this as “Papyrus doesn’t remember before”, but I don’t see it that way. Papyrus is no stranger to avoiding things that make him uncomfortable or that he doesn’t want to confront. He avoids Hotland, he seems to get depressed at the sight of the CORE and stops picking up the phone while you’re there (he says it’s because he won’t get signal there, meanwhile Toriel’s phone still rings even though it’s way in the ruins, hmm, suspicious), he refuses to take off his gloves for any reason, in a couple neutral endings he’ll confirm to you that he knows what you did and then just keep pretending he doesn’t around everyone else, he knows what the sun is and about Alphys’s lab and so many other random little things but then plays dumb or just jokes about it around Sans or Undyne for whatever reason— I think this Q&A segment is just him trying to dodge the question while also trying to spare our feelings and not outright say that he doesn’t want to answer it to be polite. He’s been put on the spot about something he doesn’t wanna think about anymore so he’s giving small seemingly inconsequential details about the place as a way to answer the question without actually answering the question.

So, wherever it is they came from (heavily speculated to be Hometown in Deltarune), he doesn’t seem to feel very strongly about returning to. He’s got new goals in the royal guard and popularity and clearly had some character development if Shut In Papyrus from Deltarune is any indicator. And they’ve already tried a ton to fix that machine and failed before. But meanwhile Sans goes on about “you’ll never see em again” and has that whole It’s Raining Somehere Else/The Place Where it Rained thing going on and the Don’t Forget image and clearly misses some people and wants to go back, so of course he’d still be keeping the key to that room because he hasn’t moved on from it!!! I also feel like a lot of the little keepsakes in there are likely Sans’s (the badge, the drawing, the photo of smiling people) and he probably goes back there to reminisce.

But yeah!

I think Papyrus is making that machine!!!

It makes sense for the guy who got out of the house to miss Deltarune and the guy who stayed in his room all day trying to make a machine to escape it to not!!!!!!