Who Might be in Sonic Movie 2? (Intro)

Since the Sonic movie did surprisingly well, and the end featured a small bonus cliffhanger, a sequel is probably a reality.

The first movie introduced us to our hero--Sonic--and villain, Dr. Robotnik. It also introduced us to Tom Wachbowski, Sonic's new human friend. All of these characters have a very high chance of returning...but will we get to see more of the Sonic cast from the games?

I'd say there are two big factors.

• In the movie, Sonic seemed to have a list of other places crossed off and said the "Mushroom Place" was the last safe place. Does that mean Sonic went else where before being stuck on Earth, or was this just a misunderstanding? 

• If he did go else where, then he may have already met some characters (and Tails knows who he is). 
• If not (and Tails has just "heard of him"), then the chances of other characters being involved are slimmer. 

• Is the next movie adapting a game(s), or is it following it's own path. 

• If only adapting one game (or even combining some into one), the introduction rate is going to be slow. 
• If they follow their own ideas (as the first movie), then it's harder to tell. They could bring characters from "other dimensions" and have a bigger plot that way, but I doubt they'd risk "confusing new viewers."    

Based on these factors and general knowledge about these characters, I'll be rating who is most/least likely to be in the next movie in my next posts...