There are only 8 distinct levels. The ninth level is a copy of level 1, the tenth is a copy of level 2, and so on. However, on the second time around the ducklings that can use the platforms and ladders are replaced by the Mother Duck, who can fly around the level going through the platforms and ladders. On the third time around, you have to face both the Mother Duck and the ducklings, and similarly on subsequent goes round, when there are more ducklings.
ESRB Rating: E - Everyone