Grillby lives up on the surface and runs a small cafe-style shop. Everyone believes he suffers from a mild case of Obsessive-Compulsive Disorder (OCD), but his issue is more severe than they might think. If something is not done just right, Grillby will resort to self-destructive behaviors to 'teach himself a lesson'. Contradicting and worsening his condition is his Tourette's, which takes his bad thoughts and perfectionist ways and destroys them.
Grillby is always wearing color-coordinated clothes. His style depends on the day, however; one day he might be wearing a suit, and the next he could be wearing a t-shirt with jeans.
Grillby is usually laid-back, and enjoys being a social butterfly. However, if he seems something is out-of-line, he can become either very aggressive or very upset in the blink of an eye.
Grillby and Sans get along well. Sans likes to go to Grillby's to vent about the fights he has with Gaster, for the most past, but will also listen when Grillby has something important to say.
He and are close; Gaster comes in every day for a cup of coffee and some small chat.
Grillby likes to talk with while they work. Though the two aren't exactly 'friends', Burgerpants may occasionally go to Grillby for advice.
Grillby doesn't know well, but he will occasionally drop food off at her house because he knows how paranoid she is of leaving.