Sans

"you never gained any LOVE. 'course, that doesn't mean you're completely innocent or naive. just that you kept a certain tenderness in your heart. no matter the struggles or hardships you faced... you strived to do the right thing. you refused to hurt anyone. even when you ran away, you did it with a smile. you never gained LOVE, but you gained love. does that make sense? maybe not..."

- Sans if Frisk never killed anyone through the Neutral run

Sans is a character in the 2015 indie-game Undertale. He is a skeleton and brother of Papyrus. He is somewhat lazy, as he doesn't really help his brother capture Frisk.

Appearance
Sans is a short and big-boned skeleton, wearing a hoodie or simple jacket, unzipped at all times, with a white turtleneck underneath, black shorts and sneakers according to his Steam trading card.

He is seen with a grin at all times, and hardly moves the corners of his mouth. He has white pupils, which tend to disappear when he is serious. A bright, flashing iris appears in his left eye during the battle against him, as well. This eye starts off merely glowing, but as he utilizes his time warping powers, it starts to flash vividly.

Personality
Sans is shown to be very laid-back, sleeping on the job as often as he takes breaks. He enjoys making bad puns relating to skeletons, to the annoyance of his brother. He is kind and reassuring, but becomes eerily serious at abrupt moments (particularly when angry).

He is also very observant, and his lines and actions change the most through the path and the way of playing the game. He knows the number of times he had defeated the player (in Genocide Route). He tends to say he hates to make promises, this is likely a result of having to harm a human, as he promised Toriel he would protect humans.

His laziness is noted again during the final fight in the Genocide route - he is unsure if being somewhat aware of the timeline resetting has broken his spirit, knowing that everything he does will mean nothing... or if he's just using it as an excuse to slack off.

Trivia

 * Sans's boss fight is widely considered by fans to be the hardest boss fight in the game.
 * Sans is the only enemy who starts his turn before Frisk does in battle, which can catch unwary players off guard.
 * According to Papyrus, Sans has a pet rock that he forgets to feed.
 * If Papyrus is killed, Sans won't appear at all until The Last Corridor. In the same case, a flavor text in Shyren's battle mentions that a hooded figure is watching the battle from afar. Given that this text only appears if Papyrus is dead, the hooded figure is most likely Sans.
 * Sans's dialogue is shown in all lowercases, not even capitalizing sentence starters and names, with a few exceptions. This probably represents his laziness.
 * If Frisk spares Papyrus instead of killing him, Sans will appear in Hotlands, selling hot dogs. The second hot dog bough will be a hot cat instead. If Frisk tries to buy one when their inventory is full, Sans will start stacking hot dogs on their head. He will do this up to 30 times.