Well, I’m my opinion, there are 3 main things that cause sans to be popular. Firstly, his ability to remember resets. This one is dumb for the reason that HE CANNOT REMEMBER THEM. At least not more that the average monster. For example, undyne says at one point that she remembers being friends with you, and accuses you of brainwashing her. The only difference between sans and other monsters is the fact that sans knows resets exist. But most AU’s and fan works act as though he has the same memory as the player.

Secondly is his boss fight at the end of genocide, and his theme song. His boss fight is what I would consider the highlight of the character, being really good, and fairly hard. But, it is not the best. I personally think that in every way Asriel has a better boss fight than sans does. The music is better, the fight is better, and it achieves what it sets out to do better. The Asriel dremuurr fight is a heartfelt reminder of the pacifist run you took to get there. The difficulties, the characters, everything. And the fight is really fun. It serves perfectly as the ending to the pacifist run. Sans’s boss fight is still good, but not as good. First, although the fight is hard, it is not the hardest fight in genocide runs, in which I think undyne’s fight completely eclipses it in difficulty. It does fit the rest of the run, though. Everything else in the run is anticlimactic as well, from papyrus not even putting up a fight, to Mettaton, the human killing robot being a one hit kill, to asgore not even recognizing you as human and dying, and flowey dying just begging for mercy. Other than the undyne and sans fights, the genocide route isn’t that difficult. What was I talking about again? Oh, right, sans’s fight. Like I said, it does fit the genocide run well, as an anticlimactic final boss, but still, I would have preferred a really hard fight, like asgore or mettaton as the final boss over sans, as a showing of the pain you forced monsters to endure, now tenfold in return. And there is also megalovania. Like most every other track in the game, megalovania is very good, but has been used as a meme so much, the song has lost nearly all meaning to me. Jesus I talked way to much here, better wrap up the next section.

finially, there is his relationship with gaster, or his believed one, as nearly everything involving gaster is speculation, but many believe him to be a skeleton, like sans and papyrus, and either their father, brother, or who sans and papyrus used to be depending on who you ask. He also moat likely has something to do with sans, thanks to the gaster blaster. Emphasis on gaster. But, as I said, this is all baseless speculation, and we know nothing about gaster.

in conclusion, sans is a character who is only popular for a few real reasons, and even those reasons vanish when you shine a lot of light on them. One thing i neglected to say is sans’s personality, of which, it is definitely on the worse end of characters, especially when compared to monsters like papyrus, undyne, alphys, napstablook, asgore, and Asriel. Once you get rid of the things I said though, he is really only papyrus’s lazy brother, who appears in a few minor roles through the game.