Play as Solid Snake
Successfully complete game 100% (all coins collected) with all default 
characters to unlock Solid Snake as a skater.
 
All secret characters:
Press Up, Down, Left, Right, Up, Down, Left, Right, Up, Down, Left, Right, Circle. A 
scream from Danny Way will be heard to confirm correct code entry. 

Level select:
Press L2, R2, Left, Right, Left, Right, Left, Right, Down(2), Up(2), Down, Up. A 
scream from Danny Way will be heard to confirm correct code entry. 

Hidden characters:
Successfully complete game 100% (all coins collected) with a character (eight pro 
skaters and one edit skater) to unlock a hidden skater. Highlight one of the default 
characters and press Circle to play as one of the following skaters. Each character 
has a different secret counterpart: 

Arto Sarri: Gorilla
Chris Senn: Gurlukovich 2
Colin McKay: Solid Snake
Danny Way: Unknown
Edited Skater: Grey 
Kerry Getz: Vampire Killer
Mark Appleyard: Raiden
Rick McCrank: Gurlukovich 1
Steve Williams: Frogger