Ubb is a playable character found in dark level 11, just before you encounter the enemy that chases you. Note: You can see his eyes glow in the lower half of the screen. Also, you must be in a local game to controll Ubb. Keep him alive until the middle of level 12, where a group of fins can be found. Ibb and Obb can die, but Ubb will remain alive and will stay on his spot.
wruby, sfbr eeaiagd

Complete the following tasks to unlock PlayStation trophy rewards.

Full Zen (Gold): Finish all levels with highest possible score.

Party (Silver): Play through all regular levels.

All Crystals (Silver): Collect all crystals from the secret levels.

Collection Complete (Silver): Find all levelmen and secretmen.

Brain Damage (Silver): Finish the game in single player mode.

First Crystal (Bronze): Collect a secret level crystal.

Small Zen (Bronze): Finish a level with the highest possible score.

Additionally there are four secret trophies.

King Ubb (Bronze): Find ubb and bring him to the next Fin City.

Quality Time (Bronze): Bounce a Fin back and forth between ibb and obb 10 times.

Fallcrobatics (Bronze): Fall through 6 different warps without touching the ground.

Mint Condition (Bronze): Finish a level without dying.