I'm going to preface this one by saying - if you're a fan of Sans, this isn't meant as hostile or anything! I'm just giving my opinion on him, and it ended up pretty long. If you want him in, then good luck!
-----
Sans
Chance: 0%
I don't often give 0%, since even if I REALLY doubt a character's chances, they could still happen. I'm making an exception for Sans - I honestly don't think he has any chance at all at appearing. Some people seem to think he's likely just because Undertale is popular, which isn't really what makes a character at all! Ignoring the fact that I don't think indies belong in Smash, here's how I think characters should work. For first-party characters, every Nintendo character, including both obscure and popular ones, should be considered - it's a Nintendo cross-over, and it's a celebration of their history! But for third-party characters, they should at least have some lasting popularity and/or importance. Cloud, for example, is very popular, and JRPGs were made more popular outside of Japan in a big part thanks to his game! Pac-Man and Mega Man are both famous, and have a huge history behind them. Bayonetta is a little different, but she got in because she won the Ballot, so there's popularity there! So there's a trend to the third-parties in that they're all popular characters with at least decent histories behind them.
To give an example of another less famous third-party I'd be OK with, I'll use Joker from Persona 5 as an example! His game is pretty recent, but it's been incredibly popular, and it's from a series that dates back over 20 years to 1996. Not only that, but it's made by Atlus, a company that's been publishing tons of games to Nintendo consoles for years, and they're owned by Sega, who has already allowed two of their characters into Smash, along with tons of trophies and other content! Another example is Arle Nadja. Her first game was released all the way back in 1989! The series she's most known for now is also popular enough in Japan that it's an eSport there, and based on fan polls, she likely did well on the Ballot in Japan! And she's owned by Sega now, so the points from Joker apply here too.
Sans is from one indie game from a few years ago that is nowhere near as popular as it was back then. Besides the game's initial explosion in popularity, there's really nothing to Sans that makes me think he's likely!
Want: 0%
I'd prefer to not have indie characters in Smash in general - if we had to have one, I'd pick Quote, the protagonist of Cave Story, since that game was one of the first big indie games ever released! It's still popular today, despite 14 years passing since its release in 2004. Undertale is a pretty good game, and I love the music from it, but I don't think content from it - Sans or otherwise - should appear.
-----
Tom Nook chance prediction: 13.68%
Nomination:
DeMille x5