The flags mean that there is a room or yellow box that you haven't been to or opened in that level. If you find all the secrets in that level, the flag turns in a crown.
If you want 100% in the subspace emissary, you have to find all secrets.
Sonic will appear during the final battle in the Subspace Emissary
A boss in the Subspace Emissary (Adventure Mode in Super Smash Bros. Brawl)
Tabuu.
Those are stickers, and they're used to power up your characters in the Subspace Emissary. You can find them randomly in the Subspace Emissary, and they also appear in versus matches.
Press up
Sonic will appear during the final battle in the Subspace Emissary
Well you can unlock most of them easily in the Subspace Emissary.
After you beat the subspace emissary, you have to go back to the swamp and there is another door there for you somewhere go to the ruins to obtain wolf, after beating subspace emissary.
You have to complete the Subspace Emissary.
In the subspace emissary mode.
It is not possible in the first game, but in SSB Melee, you have to do a 100-man melee in in Brawl Subspace Emissary.
3 ways: Coin Launcher, Subspace Emissary or if your lucky Celebi will drop it when you find him.
The rarest character in Super Smash Bros. Brawl is Mario the plumber. You can only unlock him by completing 1,000 Brawls and finishing the Subspace Emissary.
Finish the subspace emissary mode.
Unlock him through the subspace emissary.
A boss in the Subspace Emissary (Adventure Mode in Super Smash Bros. Brawl)
Tabuu.