To unlock a bonus level and one of the 6 bonus games (when you get a flower on a roullete on the end of the level), finish a world with a 100 on each level to unlock the level and bonus game. These levels are tough for beginners. Here are the bonus games unlocked in each world:

World 1: Flip Cards
World 2: Scratch 'n' Match
World 3: Drawing Lots
World 4: Match Cards
World 5: Roulette
World 6: Slot Machine