"Because... I never remembered? What? No. The music labels never..." Papyrus trails off, realizing Sans might not be talking about the obvious kind of forgetfulness. That he might mean something else.

Something like... a childhood with an awful lot of gaps in it.

The strange surprise as Sans fell apart, these last several years. After he'd done such a good job raising Papyrus, it was like he just gave up, once Papyrus was adequately self-sufficient. But that didn't make sense, did it?

He takes a deep breath, and extends an offer. "If, if something's upsetting you, right now I mean, then. There's a point to tell me. If you can. I promise, I'll do my very best to remember!" Maybe hearing that will help, as so little of this conversation has seemed to.