Undertale is one of those indie games that managed to defy the odds to reach an enormous audience on the strength of its content. Not many games, indie or otherwise, have such a devoted fan base. Part of Undertale's lasting appeal is that it's easy for fans to form an emotional connection with its lovable cast of characters.
The wise-cracking skeleton Sans is possibly the most well-known character from the game. Sans is one of the few indie game characters to appear at all in Super Smash Bros. Ultimate, fans have created endless amounts of spectacular fanart of the character, and he's a great candidate for Undertale cosplay. Here are some little-known facts about everyone's favorite punster. Warning to those who haven't yet played this to completion: spoilers ahead!
10 His HP Count Is 1
During a so-called Genocide run, where the player chooses to fight and destroy all the monsters in the Underground, the player has a chance to fight Sans. While this is inarguably one of the toughest battles in the game, it's due entirely to Sans's powerful attacks, and his ability to evade every one of the player's attacks.
Sans actually has incredibly low defense stats for such a formidable boss. If the player chooses to analyze Sans they will find out that he has an HP of only 1. As soon as a player can land a single shot, Sans will be defeated.
9 The Player Cannot Choose His Name
At the very start of Undertale, the player has the choice to name the Fallen Human. Just about any unused name can be chosen with no comment from the game, but some strange things happen when the player tries to use the names of Undertale characters.
Naming the Fallen Human "Sans" is not an option at all. If the player tries to name the Fallen Human Sans, they get a simple, Sans-like response in all lower-case just like the rest of the skeleton's dialogue: "nope."
8 He Plays Trombone
If the player chooses to go on a date with Papyrus, they find themselves in the home that he shares with Sans. Papyrus will declare with pride that he has increased the height of his sink to allow him to store more bones, but upon investigation, the Annoying Dog will be found helping himself to said bones.
Sans sticks his head out to play a brief trombone commentary on the situation, prompting Papyrus to yell at him to "stop plaguing [his] life with incidental music."
7 His Left Eye Shows His Powers
If the player progresses far into their battle, Sans will hit them with an attack that telekinetically throws them around the battle screen. While he does this, his left eye will flash blue and yellow. Those colors represent patience and justice in the game, both of which Sans makes use of in his boss battle.
Throughout the game, Sans will wink at the player when he makes a joke. If the player chooses a Pacifist run, Sans will wink with his left eye, protecting the player from his eye-powers. During the boss battle, Sans will only wink with his right eye, keeping his left eye available to use his telekinetic attack.
6 His Special Attack Is Nothing
Throughout the game, Sans, and a few other characters (especially Papyrus) will comment on his laziness. Despite working multiple jobs, tracking the player's whereabouts, and keeping tabs on his brother, Sans will insist that he is lazy.
It makes perfect sense then that his final attack during his boss battle is nothing. He simply waits for the player to get bored, even falling asleep in the process.
5 He's A Master Tricyclist
If the player successfully completes a True Pacifist ending, they will be treated to scenes of their favorite characters engaging in activities in their new lives on the surface. One of those features Papyrus driving happily down the highway in a sportscar, until Sans shows up.
Sans easily overtakes Papyrus on his tricycle. Either he's got a magical tricycle, or Sans is making use of his space-time bending abilities to lap his brother.
4 His Attack Is Related To W. D. Gaster
Throughout the game, if the player is lucky they might find references to one of the game's best secrets – a mysterious character named W.D. Gaster. This character was the Royal Scientist in the Underground before Alphys and has inexplicably disappeared from the world, foiled by one of his own experiments.
Although the nature of their relationship is never explained, Sans has a number of minor connections to Gaster in the game. One of those is the hugely destructive weapon that he deploys, should the player have to battle him. Sans unleashes multiple canons, each in the shape of a terrifying face that shoots beams of energy out of its mouth. The sprite files for these canons name them as Gaster Blasters.
3 He Breaks The Fourth Wall
Undertale loves to blur the lines between reality and gaming, and a few of its characters add to that by appearing to directly address the player. Sans is one of them.
During the battle with Sans, the player can easily die and have to restart multiple times, approaching Sans multiple times from the sun-drenched corridor outside Asgore's room. This is just one of the times Sans will comment snarkily about save files and the number of player deaths, showing he's just as aware of the game's mechanics as the player is (or maybe even more).
2 He's Left Handed
While this can't be verified, there's a very good chance that Sans is a leftie. He uses his left hand many times throughout the game when it's likely he would use his dominant hand.
These include during battle when he uses his left hand to control his psychic attack on the player, and the very first time Frisk meets him in Snowdin when Sans offers his left hand for Frisk to shake.
1 He Bends The Laws Of Physics
Several times during the course of the game, Sans will appear to teleport from one location to another. He also mentions various "shortcuts" to the player, that involve him fast traveling from one location to another. These could be dismissed as just simple video game magic, but that's not Undertale.
Sans is actually a metaphysics expert knowledgeable in the ways of space-time manipulation and the multiverse. He brings up alternate realities in conversation, as well as mentioning them during his boss battle, and there is evidence of him being involved in scientific experiments both in his secret workspace in Snowdin and the secret lab in the Core.