Well, if it's a home invader, at least they're polite enough not to stick sharp things in their gravel trap - and polite enough to offer a questioning greeting. And he's already made enough noises to not only lose the element of surprise, but to break it down into a burst of energy and some completely other elements! So Papyrus lets his hands drop from his mouth, and peers around to pinpoint the source.

"Yyyyes, hello. Welcome to, my house?"

Likely in the kitchen, he concludes. It would be in the right direction, and there's that odd food smell to the air, after all...

"Usually I expect people to start making themselves at home after I invite them in."