Frisk knew something bad had happened to him, that they'd never got a chance to meet him when they were Underground, that lots of people forgot him.

In all their time here, this is the first time they've heard any of the specifics.

"...the CORE," they blankly repeat, stomach knotting with the sight of him glitching. They don't like it; somehow, it reminds them of fighting Flowey and meeting the Amalgamates (and the entire world is ending) all at once.

They move to lean against the window's side. "...Okay. You know Sans and Papyrus?" they ask cautiously.