Board Thread:General Discussion/@comment-26006155-20200107155350/@comment-26907577-20200205182536

@THA

You got ninja'd.

@BFF

I can answer that.

Maybe all keychain-based activities are operated by Chara, who doesn't remember, but all dialogue is by Frisk, who does. And Chara doesn't know to try that last key on the chain until Frisk feels Sans tug it.

Or maybe Sans did some funky time stuff and put the key on.