I... [Papyrus goes quiet as Sans works, somehow feeling terrible after that response. It's not quite like his usual, if fleeting, feelings of guilt. But what else could such a painful, self-directed feeling with that timing be?

He wants to apologize for bringing it up, but saying so - saying sorry - would surely just invite Sans to put himself down in a joking tone some more. And this after all the work his brother did today. Papyrus really should lay off prodding him about productivity, or past lapses in it. It's only polite, as an expression of gratitude. Just a casual segue to something else...] You're right, never mind me! I-I suppose we can count your expertly crafted maze, as a thesis, soundly defended. You're welcome from me, life advisor Papyrus. Maybe I should make that my next job... [Nailed it.]