He's not sure how he feels about that.

The talking skeleton thing is weird, but he's self-aware enough to know that a taking plant is also weird. He's just not sure if Papyrus and Sans are liches or something else?? Actually being undead isn't a positive state of body to him.

He is glad that Papyrus took him seriously. He seems like a nice guy who's trusting the nightrunners to save his brother, so he's trying hard not to let him down.