This character becomes available as a playable option in Survival mode when you complete the game on the Normal difficulty and then at the 'Character' selection screen press Up(2), Down(2), Left, Right, Left, Right.
When you complete the following tasks the corresponding character wil become available. These characters can be used in Survival modes and have different stats that will not carry over if they are used in Story mode.
Unlock Boogie: Buy everything in survival mode.
Unlock Bubbles: Survive 15 consecutive waves.
Unlock Cesar: Kill an enemy with a sink.
Unlock Chop Chop: Perform 60 pistol counter kills.
Unlock Classic Shank: Kill a goon by throwing a bomber.
Unlock Defender: Perform 100 turret kills.
Unlock Falcone: Complete Campaign on hard.
Unlock Hobo: Defeat all waves of a survival map.
Unlock Horror: Reach the zombie wave in each survival map.