Adventure Mode

 Adventure Mode is a mode in SSBR. It can be used to unlock many characters. Adventure Mode is where you fight many characters in a specific order. Here's the order:

Stadium 1
Link

Princess Zelda / Sheik

Ganondorf

Toon Link

Stadium 2
Yoshi

Birdo

Stadium 3
Donkey Kong

Diddy Kong

Dixie Kong

Stadium 4
Mario

Luigi

Bowser

Princess Peach

Stadium 5
Pikachu

Jigglypuff

Pichu

Mewtwo

Pokemon Trainer

Lucario

Stadium 5
Fox McCloud

Falco

Slippy

Wolf

Stadium 6
Goku

Vegeta

Piccolo

Frieza

Krillin

Stadium 7
Aang

Katara

Sokka

Toph Bei Fong

Zuko

Stadium 8
Solid Snake

Gray Fox

Sonic

Tails

Knuckles

Shadow

Secret Stadium
Unlocked by doing certain requirements. (Ex: Beat Adventure Mode with Mario and Bowser to make it to Luigi's secret stadium)

Videogame Land
Pac-Man

R.O.B.

Mr. Game & Watch

(It is unknown how to unlock Videogame Land yet.)

Links
Adventure Mode's blog post: http://ssbr-dojo.blogspot.com/2011/01/adventure-mode.html