As a playable character,no. The character Sonic is there, but is locked. Knuckles appeared as a collectable trophy :)
he`s not there
No. You can play as Sonic, but not Knuckles. Knuckles is however available as a trophy, or can be seen running along in the green hill zone stage.
You can get a knucklehead if you stand still when you fight the Master Hand. But they have no reason to put Knuckles in the game. Shame.
NO. I have every character, and he isn't in it. However, he is on the online version
you cant unlock knuckles
The Coin Launcher, trophy boxes in the Subspace Emmisary, and occasionally, in Home-Run contests.
Sonic is in SSBB.
rosalina is not a character in ssbb
You can't get tails in SSBB.
he is not a playable character in ssbb
No. You cannot get Darkrai in SSBB, even with hacking.
There are no looney tunes characters on SSBB.