One minute, Papyrus is staring at his brother's strange, fearful expression. What could he possibly have said to inspire that? The next minute, he's staring at a rack of glass vials. That teleportation trick is bad enough when it's used for pranks, but running away from a strange conversation? That's a new low.

At the crashing sounds, his head around, and he sees Sans staggering over some more of the fallen objects. "Sans! What was that??? Are you..." Wait, no. He stops halfway through that question, as it's obvious that Sans isn't all right. Instead Papyrus pushes away from the counter, walking across the room towards his brother.

"...Is there anything I can do to help? You're starting to scare me." If the answer is something like 'go away,' he'll need to politely refuse. Leaving his brother completely alone here seems like a bad idea. But... if they could get back home, or to Grillby's, or something, he'd be willing to let someone else keep an eye out on Sans.