Sans is a short skeleton. He has a sweating skull with a crack at the top (it's a mystery why he has it), two eye sockets, with the left one having a glowing red eye bags under the eye sockets (due to lack of sleep), a nose, and a smiling mouth with sharp teeth and a yellow tooth on the left. He wears a black unzipped jacket with a white hood, red shirt, black basketball shorts with a yellow line of the side of them and red sneakers.
Sans is not into puns that much, but he likes knock knock jokes. He often gets tired, but not flustered. He strives to be collect and cool. He loves mustard and relish. He once tried wearing Papyrus's boots and felt alive.
- His sweat used to be an aesthetic, but Underfell's creator then changed their mind and made it canon that Sans sweats because he's hot under his jacket.