[It's almost like he's starting to get it. Almost.

They don't think he has it in him, to think they'd plot something so diabolical. Maybe. At the least, he seems to believe the real Frisk has something better in them. Not dealing with the most confrontational demon, the most aggressive. Get's to respond passively in kind.

Gets to use a pun and pretend it's just another joke.]

You like to tell them how it's all your fault they think like they do, Sans. The part where they want to die isn't your fault...mostly.

[A soft sight. As if losing interest, they turn away; pull a ladle out of the drawer, and begin spooning boiling hot mud onto a baking tray.]

The part where they think they're a huge joke? That's you.