This game has a hidden level select.
Depending on who you ask, the Krazy Kreatures might not be as 'krazy' as you think.
Extended Level Select
Start a new game. When the Kreatures start to appear on-screen, pause the game, hold the A button, and press Select 10 times. Lose the game, and return to the options menu. The level select option will now be able to go up to Level 24.