A familiar figure, no doubt. His hostility is kept to a minimum, as befits everyone. It is unlikely he would be restrained should he be genuinely hostile - though assumptions, as all well know, are unkind things to be made regarding those whom they do not know.

All the same, there are some that may find a silent observer to be - unsettling. Not Frisk, of course; they bear no qualms about Sans's tendencies, neither here nor at home. But others may take umbrage with such a thing.

Others may approach with the casual, dismissive lift of an eyebrow.

"Enjoying the view?"