The look that Sans gives this new stranger is sharp.

He's not sure what to expect out of this, but the dreamlike quality of the scenario has him more frustrated than curious. He absolutely doesn't want to deal with whatever is going on here, and he has no idea what this other skeleton is going to want out of him. As one skeleton in a lab, another one appearing doesn't seem that special. This is probably some kind of memory - this person is probably more of a phantasm than an individual.

And so, instead of asking questions or even responding, he stares right at them and then slowly pushes a small rack of test tubes onto the floor. Smash.

"What's it to you?" he asks blandly.