I assume that it'll be models already in the system - meaning, because Shadow is an assist trophy, he's usable. Just like the stage for Sonic - Knuckles, Tails and Silver (FUCK YEAH I LOVE SILVER HE IS SO THE BEST) are in the background.
Tsunami Bomb - The Simple Truth
We could run away
Leave behind anything paper
Not knowing where we're going to stay
When there's no Mondays
You're part of me, it's so easy to see the simple truth
When I'm in your arms, I feel safe from harm and sorrow too
You're part of me, it's so easy to see the simple truth
But most of all, nothing couldn't be solved when I'm with you