That comment sounds like a pun and like the speaker has been eating bones. Not quite the worst possible first impression, but close to it.

Papyrus groans as he turns, asking, "Is Sans giving you bones? Because if I told you once, I've told you..."

He frowns at Xanxus, and peers around like he expects there to be someone else behind them. But no,they're the only apparent source of that comment. "You don't look like a dog. Do humans eat bones, too?!"