Sans

Sans Undertale, formerly known as Ness Earthbound, is the mascot of senok and a major character in Undertale. He's the most popular character in Undertale, and he appears in more media too, such as Super Smash Bros. Ultimate. He has two brothers, Papyrus and Wide Latin, the real character, and has an unknown relationship to Dr. W.D. Gaster. But there's totally something there.

Personality
Sans is a lazy son of a mother who spends all his time just like doing nothing. His lifestyle is admirable. But also it may be because he's aware his entire reality can be reset to nothing, making all of his actions pointless, so that's kinda a huge bummer.

He might've been a scientist before or something. He likes sci-fi according to Papyrus. He gets all serious on the Genocide Route but seems to genuinely like you on the Pacifist Route. Understandably.

Appearance
Sans is a short skeleton almost always in a blue hoodie, white shirt, black stripey shorts, and slippers that are either pink or white. He has eyebags and black eyes with white pupils, a bit of his legs are visible and maybe his neck I dunno what is that even. Also he smiles all the time.

Papyrus
Papyrus is Sans' favorite brother named Papyrus. Sans likes Papyrus even though he annoys the hell out of him. Isn't that what siblings do, really? Sans also always comments if you kill Papyrus in Undertale, even though he only actually fights you on Genocide for some reason.

senok
Sans might be senok. No one really knows. senok thinks Sans is really cool and epic and swag money and cash money though. Man, isn't senok just the best?

Wide Latin
Wide Latin, the real Undertale character, is Sans' brother. Is he younger or older? Who knows. Sans has absolutely no opinion on him, somehow. You'd think Sans would know how it feels to be an epic gamer like Wide Latin, but Wide Latin plays Fortnite and Sans plays Minecraft, so he feels it's completely different.

W.D. Gaster
✡︎⚐︎🕆︎☼︎ 💣︎⚐︎💣︎ ✋︎💧︎ 🕈︎📬︎👎︎📬︎ ☝︎✌︎💧︎❄︎☜︎☼︎ ☹︎💣︎✌︎⚐︎ ☝︎☜︎❄︎ ⚐︎🕈︎☠︎☜︎👎︎ ☟︎✌︎☟︎✌︎📬︎

Geno
Geno is a long time friend of Sans' who he met back when he was Ness. They met back up during Undertale. At first, Sans didn't remember who he once was, but Geno recognized him and reminded him of the events of Earthbound. Sans quickly remembered and hung out with Geno and introduced him to Papyrus and stuff.

Toriel
Sans is literally just friends with her shut the fuck up.

Frisk
Depends on the route. In Pacifist, Sans likes Frisk, thinks they're pretty chill, and only makes a couple creepy comments sometimes. In Genocide, he like hates them but acts really calm about it for some reason, like dude they just killed everyone you love why are you so chill. He's not even really affected by his own death.

Ness' Mom
Ness' Mom is Sans' mom from when he was Ness. He's completely lost contact with her but he vaguely remembers her.

Ness' Dad
Ness' Dad is Sans' dad from when he was Ness. Geno knew him, and he tells Sans how he's doing sometimes.