Though masculine in programming (masculine used lightly), he was described in the Netural years episode Hanger 18 as being a "hermaphrobot" which was really an elaborate joke by Frisk. Sans is easy going, but snarky, quick-witted and opinionated. He often delivers the most sarcastic remarks and is the biggest quipper in the AU.
Sans uses cyber-based bubble memory, works off UNIX and can use a variety of operating systems, underwent a complex personal evolution wherein painful confusion has given way to what he likes to think of as some degree of wisdom culminating in his current Zarasthustrian sense of self, often panics when making sandwiches, smells conspiracy in everything and doesn't know what he means most of the time. Sans's accomplishments during the show's run include writing several screenplays, including Earth vs. Soup (his seminal work), Peter Graves at the University of Minnesota, The Spy Who Hugged Me, and Chocolate Jones and the Temple of Funk, as well as a satirical political musical called Supercalifragilisticexpiali-wacky!. He is also an avid member of the Kim Cattrall fan club, although he later harbors some affection for Estelle Winwood. Sans holds the distinction of being the only Bot who ever visited Deep 13 (although Papyrus Servo and Toriel once visited the alternate-earth version). In Kitten with a Whip, he slid down the Umbilicus in an attempt to bring the SOL back to Earth, but he retreated back up to the satellite after he was frightened when he got caught by Dr. Gaster (who then had Alphys put a giant mousetrap beneath the Umbilicus—only to accidentally set off the trap on himself), standing next to him (So close). In the "Turkey Day" version of Night of the Blood Beast, Sans attended the Gaster Thanksgiving dinner alongside such guests as Mr. B. Natural, Pitch the Devil, and others. A second Sans lives in Wisconsin working at a cheese factory, due to a time paradox during the Time Chasers experiment. During Fire Maidens of Outer Space, Sans acquired a double named "Timmy", whom the trio quickly took a liking to; however, the double began playing tricks on Papyrus Servo and Frisk, who blamed Sans for the actions. He eventually joined them in the theater during the movie and attacked Papyrus, cocooning him in a matter identical to the xenomorph from Alien, forcing Frisk and Sans to stuff him into an airlock and blast him out of the ship and into space. Timmy's appearance was a parody of the evil twin concept. In reality, Timmy is the black-painted Sans used for the Shadowrama during the Theater segments.
He doesn't fall hard in love the same way Papyrus Servo does, but he has his odd little crushes every now and then. In the Season 3 episode, City Limits, it's revealed that he's attracted to Kim Cattrall, until one year later, he became infatuated with Estelle Winwood during the Season 4 episode, The Magic Sword. He's also implied that he may to be attracted to Servo, even having a weird dream of him in a nurse's outfit. In Racket Girls, Sans is inspired by the short Are You Ready for Marriage?, asks Chara for Papyrus Servo's "hand-in-marriage". Later during the wedding ceremony, Dr. Gaster, as a wedding priest/preacher, and Alphys, as the guitar player for the occasion, tries to attempt to carry out the wedding mass, but they suddenly ended up having the wedding guests disrupt the session during the event by having everyone punching each other, causing Chara and the 'Bots to begin to start wrestling violently, ruining the wedding, and everyone pretty much forgets about the short in favor of the movie. Sans is somewhat prone to injury, as he gets blown up or attacked quite a bit during the series' host segments. Likewise, he's also sensitive to vertigo, as he experienced nausea and dizziness from the unusual layout of the credits for Warrior of the Lost World and Beginning of the End.