[Frisk smiles serenely as they continue playing with the Dagger with pointed indolence, turning the long blade over and over in their hands. He's lost so much of his pomp and egomania, hasn't he? Yes, it didn't take very much to strip him of that, did it?

And there they'd been thinking of just killing him and being done with it. But why would they ever do that when instead they could drive a stake in his SOUL, tear apart whatever saccharine friendship he and the Real Frisk have established?]

You really should take better care of your things, ghost-bot. Throwing something like the key to your home away was a very poorly-rationalized move.

[Especially when it's well-known that monsters regularly rummage through the human garbage that falls in from the surface! Really, Mettaton, they're horribly disappointed in you.]

Pretending a key isn't there doesn't make it go away, you know.