In terms of plausibility, these theories range from extremely likely to the infamous Sans is Ness theory. A theory so wrong that Toby Fox himself de-confirmed it on X (formerly Twitter).

Undertale's Sans beat Reigan Arataka from the anime Mob Psycho 100 in a Tumblr Sexyman poll, and Undertale creator Toby Fox wrote lore for the event as a result. Still with us? Fantastic.

It was an extremely close competition in the end, with Sans beating Reigen by less than ... it’s a genuine delight to see Fox recognize the fandom that’s still alive and kicking long after ...

Toby Fox’s “Megalovania” may be known as a five-year-old video game banger, but the meme behemoth actually has a more layered history. Famous for its association with Sans, the funky ...

He's surprised when Sans, who was entered in the contest unwittingly ... and it's great to see a storied developer like Fox poke his head up randomly to beef up the lore of what is, essentially ...

Undertale creator Toby Fox has made no secret of the fact that ... So the people who were interested in Ness could search online and instantly not only find answers, but people espousing that ...