[Papyrus laughs at the joke despite the tone, like the mean edge is going past his notice - or at least his caring.] True enough! I appreciate it, those may come in handy sooner or later.

[There's no mean edge to his voice, no sarcasm. Appreciation, a bit of pride in Sans's initiative, a little congratulations to go with it. All the things he might normally sprinkle onto an expression of gratitude, the better to encourage Sans to keep them up. And the lack of mean edge continues, even as he says:]

If you're not sleeping well, want to go star-gazing? It's the perfect kind of night, you said. Clear, no lights...