Press select to go to the inventory screen, then press square 6 times, then circle, up, circle, left, circle, right, circle, then select to go back into the game, and you lives will now go up to 99.
This trick works for any world and in any level except the home levels. If you fall off a cliff, ledge, etc., You can just hit pause and exit the level. This way you end up at the portal to that particular level in the home level, and have saved your life.
During gameplay pause and go to the inventory screen. Now press Square, Square, Circle, Left, Right, Left, Right, Circle, Up, Right, Down. When you go to a balloonist you'll have access to all levels.
To get this level, you must successfully beat the game with 100% at the end. Then, go to Gnasty's World and walk up to the green dragon head. This head will open and reveal a secret level called Gnasty's loot.
