The profound weariness on Sans's face in response to that offer is clear, and not just because Papyrus was just trying to drug him with magic dust. He's still testing his eyes, blinking them heavily in an effort to stay focused, but right now taking a nap would be so much easier than dealing with this shit.

"Bro... You know I really don't want to get my head messed up again," he says, exhaling slowly. He can't see any way out of this that isn't a confrontation. "That just sounds like it'd be asking for it. As much... as I know you want me to understand right now."

This is stupid. He already knows, from experience, that there will probably be no convincing Papyrus of anything when he's like this. Sans doesn't know the objective truth, but he knows that giving up on people like this isn't what his brother has been about. Basically ever.

"You never would have given up on everyone like this on your own. That's supposed to be my schtick, right?"

Please, please just go back to being normal.