The Subspace Emissary
The Subspace Emissary (Japanese: 亜空の使者 The Subspace Emissary) is a single-player game that is contained within Super Smash Bros. Brawl. It is a side-scrolling action game with a storyline that is said to emphasize character development. Most of the playable characters are protagonists, including Pokémon universe characters Pikachu, Pokémon Trainer, and Lucario. Jigglypuff also appears, but only after completing the game's plot and has no role in the storyline.
The characters form teams based on the development of the story. All hidden characters can be unlocked by simply playing through The Subspace Emissary, though three of them (including Jigglypuff) only appear through secret doors that appear after the main plot has been completed. A second player can join in at any time, though the camera will focus on player one. Like Classic Mode and All-Star mode, the difficulty level can be changed, but unlike those modes, the difficulty level can be altered after the challenge has begun.
In order to obtain trophies of the enemies in this game, the player must throw a Trophy Stand at them. This acts similarly to a Poké Ball, as it 'captures' the opponent only when they are at low health. Trophy Stands also work against bosses, such as Rayquaza.
Plot
Led by a being known as the Ancient Minister, the Subspace Army's plan is to cut apart the world and carry it into Subspace. This is achieved by two R.O.B.s detonating a Subspace Bomb and the minions known as Primids, which are created from Shadow Bugs from Mr. Game & Watch, attacking anyone who resists. Now everyone must team up to stop this threat. After finding the Ancient Minister, who turns out to be a R.O.B. in disguise, all the Subspace Bombs in the factory detonate, creating a portal into Subspace from which Ganondorf and Bowser emerge on a giant battleship. The characters of Super Smash Bros. Brawl team up and enter Subspace, where they see Master Hand enslaved by the Chains of Light. Master Hand crashes to the ground just as a mysterious being known as Tabuu emerges, revealed to be the ultimate master of the plan. Tabuu attacks with his wings, turning all the characters into trophies. A select few characters later awaken due to the effects of the Dedede Brooches left behind earlier by King Dedede as a backup plan. They proceed to pick up the fallen trophies of the other characters, reviving them. The player then must traverse the entirety of the final stage known as The Great Maze, consisting of joined pieces of the outside world that Tabuu has constructed in Subspace. Once the player has defeated every major enemy in the maze, the door to Tabuu is unlocked. Once again, the characters confront Tabuu. He is about to turn them into trophies with his wings again, when Sonic shows up, tearing through Tabuu's wings, severely weakening them. Once the player defeats Tabuu, the credits roll. After both The Subspace Emissary and Classic Mode have been cleared, Boss Battles can be unlocked.
Rayquaza
Separated from Donkey Kong, Diddy Kong sees an Arwing get shot down by a blast from a nearby lake. Upon reaching the lake, Rayquaza emerges from the water and captures Diddy Kong, but Fox jumps out of the ship and makes a dramatic rescue. Rayquaza then attacks Fox with Dragon Pulse, but Fox reflects it back at Rayquaza. Fox and Diddy Kong then fight Rayquaza.
Along with the other bosses in the game, Rayquaza is fought again in The Great Maze, and can later be challenged in the Boss Battle mode.
In battle, Rayquaza can use a variety of attacks, including Thunder, Dig, Fly, Tail Whip, ExtremeSpeed, and Dragon Pulse.
Pikachu
While searching for her stolen Power Suit in The Research Facility, Zero Suit Samus discovers Pikachu, whose electricity is being harnessed for the facility's power in a capsule-like machine. Seeing the pain it causes, Samus uses her Paralyzer Whip to free it, destroying the machine and sounding an alarm. Pikachu and Samus travel together throughout the facility and The Subspace Bomb Factory.
Pokémon Trainer
Lucas bumps into the Pokémon Trainer at The Ruined Zoo. They decide to team up to help rescue Ness from Wario and help the Pokémon Trainer capture Ivysaur and Charizard. The two travel together throughout most of the game.
He starts out with only Squirtle, and later captures Ivysaur and Charizard at The Ruins.
Lucario
At the top of a snowy mountain, Meta Knight and the Ice Climbers encounter a meditating Lucario. After a short battle that unlocks Lucario, he helps Meta Knight in his mission to recover his stolen battleship Halberd from a horde of Mr. Game & Watches.
He later uses his aura to detect Snake hiding in a box and an approaching enemy threat. Lucario rescues Princess Peach, Princess Zelda, and assists them along with Falco and Fox in fighting Duon, who is based on Dialga and Palkia.
Jigglypuff
After beating The Subspace Emissary, the player can return to The Swamp and locate a door that did not appear before. Upon entering the door, a cinematic shows Jigglypuff singing at Pokémon Stadium 2. The player then fights Jigglypuff. If the player wins, Jigglypuff joins the party. Other than this, Jigglypuff does not play any significant role in the story.