As we see at the end of Chapter 2 in Deltarune, before creating the new fountain Kris opens the door. This would be a weird behaviour if we didn't know that Toriel had called the police station about someone slashing her car wheels, which meant Kris overheard this conversation and prepared for their arrival. But we must first put in some consideration before jumping to the conclusion that it is 100% going to be Undyne.

• If Undyne WAS in the dark world, she could act like Berdly and join the "bad side" without knowing it. By my prediction of Toriel becoming a party member, and Undyne hating fire and heat (which Toriel's magic is based upon), this could be another Snowgrave. But Toby knows that the same gameplay with new locations would get boring pretty fast, so it's a possibility he might not add Undyne for that reason.

• Napstablook is a police officer too, and he is one of the most unspoken and unseen of the main characters in either game from my POV, so I feel Toby might add him instead of Undyne to give him a bit of the spotlight.

• It is not shown who Toriel talks to at the end of the chapter, and that means it is still up for questioning.

  Just think about these for a while. Also as a side-note, since Undyne and Napstablook seem to be the only workers there, that means one of them must stay behind to take any more calls that come through.

  Anyway's as a little bonus for reading all this have my version of "dark world Napstablook" and thanks for reading!!! :)