NOTE: Stickers and assist trophies appear at random on the stage, that much is still true. The ones listed below WON'T appear randomly until you unlock them. Once you do, its anyone’s guess when they will appear in game, just like normal.
Barbara
Square:
Requirements:
1) Unlock 25 songs.
Custom Robo
Square:
Requirements:
1) Play 100 Versus Mode matches.
Gray Fox
Square:
Requirements:
1) Unlock Snake.
1.1) Play 15 Versus Mode matches on Shadow Moses Island.
1.2) Play 130 Versus Mode matches.
1.3) Have Snake join you in the Sub-space Emissary.
Infantry and Tanks
Square:
Requirements:
1) Play 300 Versus Mode matches
Isaac
Square:
Requirements:
1) Play in 200 Versus Mode matches
Shadow the Hedgehog
Square:
Requirements:
1) Unlock Sonic
1.1) Play 300 Versus Mode matches.
1.2) Have Sonic join you in the Sub-space Emissary.
Boo (Mario Tennis)
Square: B:4
Requirements:
1) Hit Sandbag a combined total of 900 feet in the Homerun
contest.
Liquid Snake (Metal Gear Solid: the Twin Snakes)
Square: D:16
Requirements:
1) Defeat 10 enemies in Cruel Brawl.
Phyllis (Animal Crossing: Wild World)
Square: B:17
Requirements:
1) Clear All-Star on Normal.
Running Chibi-Robo
Square: B:11
Requirements:
1) Clear Classic Mode on Easy.
Ryuta Ippongi (Ous! Takae! Ouendan 2)
Square: A:6
Requirements:
1) Clear 100-Man Brawl in under 3 minutes, 30 seconds.