If Lambert had to describe Papyrus, he would say he's a simple guy with complicated problems. Lambert can't claim to fully understand the whole time loop situation thing, nor does he truly want to -- that's a problem way above the witcher's pay grade. Besides, it sounds like Papyrus and Sans are on it already!

Despite a fiery first introduction, Lambert and Papyrus have lapsed into a bit of an easy relationship, mainly because Papyrus never seems to be bothered by Lambert's more acerbic moments and is sort of just persistently friendly to the point where attempting to dissuade it would be futile. Knowing some of the skeleton bros' backstory from both sides now, he isn't sure whether he could consider Papyrus a fool or astonishingly persistent ... or both, really.

Lambert regards Papyrus a little warily sometimes, in the vein of no one's always like that, always and he's just waiting for the skeleton to snap one day, but so far, that doesn't seem likely. So it seems like he really will just have to accept that the skeleton is like that! He enjoys hanging around Papyrus when he wants relatively uncomplicated interactions, but he's a big much to hang out with just shooting the shit (idly wonders about drunken Papyrus, though, and what that would be like). It's hard not to respond to someone who seems so genuinely happy to see you all the time, and who never seems to expect anything from you but your company.