At the "white" Konami screen, press Up, Down, Left, Right, Up, Down, Left, Right, Up, Down, Left, Right, Circle to unlock all secret characters. If you entered the code correctly, you will hear a scream from Danny Way.
Kid mode
To unlock Kid Mode, successfully complete all goals in practice mode.
Level select
At the "white" Konami screen, press L2, R2, Left, Right, Left, Right, Left, Right, Down(2), Up(2), Down, Up. If you entered the code correctly, you will hear a scream from Danny Way.
Play as Solid Snake
Beat the game with all default characters to unlock Solid Snake as a skater.
Secret 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
All secret characters...