Sans

Sans is one of the characters in Underplot. He makes a cameo in Harry Pothead Chronicles S1E3.

He is extremely lazy, and constantly skips his duties. Despite this, he seems to get along with everyone.

A character who shares an uncannily similar appearance to him is a secret boss in The Adventures of Lifing. However, that's John Skelleyton, a completely unrelated character.

Personality
Sans is friendly and constantly cracks jokes. His favorite form of humor is puns, much to his brother's annoyance. He can also be serious, but not unless he needs to.

Trivia

 * He interrupts the video for a commercial break, where he asks the viewer to buy Undertale to support its developers. This puts him on a level of conscience above even Insta, since he is able to recognize the franchise he is a part of.
 * He makes a cameo in Harry Pothead Chronicles, but there, he pronounces Undertale as Undertalé.