The Subspace Emissary

The Subspace Emissary is the Adventure mode in Brawl. It tells the story of the Subspace Army, led by the Ancient Minister, and its attempt to bring the world into Subspace. The story includes most of the playable characters featured in the game and intertwines their worlds so that they meet and interact. Most levels appear to require the player to choose between one of a few characters that are available. There is also a Co-op mode that allows two players to play at the same time. Most of the enemies in the Subspace Army make their debut in Brawl, while most of the bosses have appeared in previous Nintendo titles.

Link's Role
Link appears in a forest and teams up with Yoshi. Depending on which princess was saved, Link will either confront a mind-controlled Peach or confront Mario and Pit after seeing Zelda supposedly dying. They later team up and track down King Dedede.

Zelda's Role
Zelda can either be saved or captured by Wario in the beginning. If she is saved, she will journey with Kirby only to later be captured by Bowser after Kirby leaves her behind. If she is captured by Wario, Shadow Bugs will create a replicate of her, which Mario and Pit have to defeat. She, along with Peach, is later saved Solid Snake and transforms into Sheik.

Ganondorf's Role
Ganondorf reprises his villianous role and helps the Subspace Army by following Master Hand's orders and even betrays Bowser by turning him into a trophy. It turns out that Master Hand was being controlled by an entity known as Tabuu. When he attempts to attack to Tabuu, he is simply turned into a trophy. If Link and Zelda are revived, they will reawaken Ganondorf and force him to work with the group seeing as much damage he has done.

Toon Link's Role
Toon Link does not have a role and only appears if you enter a secret door in the forest after clearing the Subspace Emissary.

Enemies
Other than Goombas, Koopas, Hammer Bros. and R.O.B. all the enemies in the Subspace Emissary are completely original and made for the game.