Wow. I did not expect that last bit at all, but it is a welcome one. I also love the fact how undyne just said "you are dead to me" other then just start throwing spears around like everyone else makes her do. That line put a chill down my spine from how unexpecting that was. Nicely done. A very "bone" chilling experience if I say so myself.
15:04 – It's curious to see that Papyrus in your reaction is definitely aware of what's gonna happen there and recognises it from the first word he says
FINALLY SOMEONE ELSE THAT MADE THEM WATCH THE GREAT PAPYRUS
but out of joke or hype i love it but maybe you can show them "PAPYRUS NEVER MOVE" is a nice theory and it would be nice to show them how papyrus is kirby and shaggy power typo