User blog comment:NOS Sterling/Sonic Boom could bring two more fan favorite characters/@comment-3964768-20140814011838

In other words, Shadow and Metal Sonic. That said, I doubt Metal actually appearing. His apperance in the trailer could've just been a placeholder, after all.

I'd like to see some of the one-off characters that SEGA keeps forgetting about, if only due to it's "fan"base. Characters like Shade and Tikal. Or even Tiara with a possible redesign. After all, there is literally no reason whatsoever that they can't bring her back, unlike Shade.

That, or they have a contest to see if fan characters could cameo in some of the episodes. You know, for a laugh.