Technically speaking, out of the main cast in modern the Sonic series—only 9 “relevant” characters remain to be playable.

Kind of hard to put it into a title but what I meant it that these characters in the screen are the “main cast” or “relevant characters” in the Sonic franchise currently. These characters are relevant because SEGA is still using these characters for the Sonic franchise to this day. There are 20 characters here, 9 of them are the only ones not in the game as of right now.

I don’t wanna apply pressure to the devs, this post is just a fun-fact.