[Between the shared laughter and the suggestion, Papyrus gets an impression less of someone instigating the sibling rivalry, so much of someone who's been pranked by Sans and is now interested in a little payback. He nods in appreciation of this maybe-not-accurate characterization, and considers the suggestion.]

More decorations for the tree... That's a great idea! And great for looking on the bright side, of winding up here. The tree could use a few more lights... And maybe a string or three for the fence.

[There's the slightest punning emphasis with those italics, there. If there aren't a lot of closed curtains on Loomis Drive yet, it's surely only a matter of time.]