Sans

Sans is the true hero of the videogame "Undertale", sharing the role with Undyne, the head of the Underground's Royal Guard. He was a major keystone for The Merger Magikoopa's plan to have his own timeline.

Appearance
Sans is a short Overlander skeleton with a dimpled smile, large eye sockets, and perfectly aligned teeth. He wears an unzipped blue hoodie, a white t-shirt, black shorts with white stripes, and a pair of sneakers. He has white pupils that disappear when he is serious or angered. In battle, Sans's left eye glows blue, and his right pupil disappears. As a Chaos Demigod, both his eyes glow blue.

Biography
When Sans was very young, he experienced major losses, as his mother died, while his father, Dr. Gaster, was sent into a dimension known as "The Null Space", into an accident. Sans was only left with his baby brother, Papyrus.

At an unknown point in the past, Sans became a scientist and started to make research on quantum physics. At some point, the Genesis Waves (along the Super Genesis Wave) occurred, and Sans noticed them as an anomaly in the time-space continuum.

After the first Genesis Wave, one of Sans's coworkers, Dr. Alphys, revived the lost prince of the Underground as Flowey the Flower. Flowey started to try and kill the monsters whose prince he was, only to be stopped by Sans. Flowey, however, had the ability to reset timelines.

After the second Genesis Wave, an Overlander named Frisk fell in the Underground. Originally with good intentions, as they wanted to save the monsters from the Underground, Frisk had an "all or nothing" philosophy. After becoming the only person who knew Flowey was actually Asriel Dreemurr, the lost prince of the Underground, Frisk tried 123 times to make Flowey become Asriel again, only to always fail. They eventually gave up and started killing all monsters. Sans didn't knew about Flowey's real identity, and assumeded that Frisk is "the type of person who won't ever be happy".

After fighting and being defeated by Frisk 4822 times, Sans met up with the Merger Magikoopa, and teamed up with him in a win-win deal, minutes before Drs. Eggman and Willy unleashed the Super Genesis Wave. As the Merger Magikoopa knew Eggman would try to stop Super Sonic from fully resetting the Prime Zone and Mario would stamper Bowser Jr.'s "Operation: Clean Sweep", he called for Sans's help. He promised Sans to bring his parents back. In order to stop at least Eggman, the Merger Magikoopa gave Sans his soul, which was as powerful as 7 Overlander souls, practically turning Sans into a Chaos Demigod. Sans then reset the Super Genesis Wave, not without being distracted by the battle between the two doctors and their archenemies. Because of the distraction, the reset had many side effects, but Sans ended up in a timeline in which he had his mother as guardian angel, Frisk was still a pacifist and Undyne was a Sonic fan. This timeline seemed more enjoyable for Sans and, as the Merger Magikoopa knew Flowey's real identity, Asriel was ensured to return, which meant Frisk wasn't going to do another reset after the Pacifist Run would end.

Personality
Sans is laid back, often sleeping and taking breaks. His laziness is a combination of fatalism and apathy. He wonders if his indolence stems from his knowledge that any progress he makes will be erased by the next reset. Conversely, he suggests that this knowledge could be "a poor excuse for being lazy."

Though Sans is usually agreeable, he becomes eerily serious at particular moments. He is also observant. He enjoys making skeleton-related puns and he may be a talented comedian. He enjoys science fiction and loves to drink ketchup. He also hates making promises.

Sans has a scientific background. Evidence includes his quantum physics book, his workshop, his work relationship with Dr. Alphys, his affinity for science, and his research on the Genesis Waves.

Powers and abilities
Sans can quickly travel or teleport using what he calls "shortcuts."

In combat, he uses "Gaster Blasters," devices that resemble a skull, to shoot large beams. Sans excels in combat and fights with unique abilities that include: KR, applying directional forces directly upon his foe's soul, and attacking his foes in their own selection menus.

Thanks to his research, he has the knowledge of timelines and Genesis Waves. His mind seems to be immune to the effects of the Super Genesis Wave. His awareness of time travel makes him scrupulous.

Like most monsters, Sans can absorb Overlander souls, becoming a Chaos Demigod. Sans can absorb a maximum of 7 souls. As a Chaos Demigod, Sans has boosted stats and can reset timelines.

Sans can also play the trombone.

Trivia

 * Sans's name alludes to a font used on Internet Word, font known as "Comic Sans". This may be a reference to his liking to make puns.
 * Contrary to popular belief, Sans actually has more than 1 HP. Evidence is the fact that, on Frisk's Genocide Route, there is a kill counter, which can go up to 105. The 105th enemy is killed shortly before battling Sans, meaning that Frisk defeated but never killed Sans.
 * Since Frisk deals 9'999'999 damage to Sans in one hit, it is possible that Sans actually has 10'000'000 HP.
 * This number can go even bigger if Sans becomes a Chaos Demigod.
 * 9'999'999 damage would stun any mortal. Meaning that, after dealing Sans the blow, Frisk just thought they killed him, when he was only unconscious.
 * It wouldn't have mattered, anyway, as completing a Genocide Route would lead to the erasure of the world. Sans would, however, wake up in a new world.
 * It also leaves a cut across Sans's chest, from which a red fluid was leaving. Whether it is injected determination or actual blood it's unknown, but it is certain that Sans wouldn't live much longer anyway.
 * It may be possible for his large amounts of HP to derive from his laziness, as sleeping increases the maximum amount of HP one can have.