no, however you can unlock him in super smash bros. brawl
Sonic Underground is an animated TV series. And no, you cannot unlock episodes, or characters other than Sonic, from Sonic Underground in Super Smash Bros Brawl.
No, Super Smash Bros Brawl for the wii is the first one to feature Sonic.
If you're thinking of the Sonic Riders character, you cannot unlock him in Brawl.
all you have to do is beat tabuu in the end of subspace. be aware! he is even very hard on easy mode!!! I unlocked Sonic in brawl by getting a score of 15 in a time brawl. I would recommend having the score display on, if you've unlocked it. I got it by completing 20 classic modes with different characters
By completing SSE (Subspace Emissary or Adventure Mode.)
There is no Silver in Super Smash Bros. Brawl. Sonic is the only character from his series. Maybe in the next Super Smash Bros. game.
No, in fact Shadow isn't even in Super Smash Bros. Brawl. He is from the Sonic games. Sonic however, isn't from Super Smash Bros. Brawl but Sonic is in Super Smash Bros. Brawl.