Cheepskipper

Cheepskipper is the boss of World 3 in New Super Mario Bros.

Cheepskipper is a purple and white Cheep-Cheep with yellow fins and specks. The fish also has a large mouth with two large frontal teeth.

In the battle, Mario or Luigi must defeat Cheepskipper by jumping on it three times. However, it is only vulnerable when it comes out of the water to attack. It jumps out of the right, bounces along the bridge, and exits from the left. The player must step on it before it goes beneath the bridge to apply damage. Also, Cheep-Cheeps are constantly jumping in and out of the water during the battle, and cause damage if touched by Mario or Luigi.

Access to World 5 is earned after Cheepskipper is defeated.

Trivia

 * Cheepskipper's character design resembles Boss Basses from Super Mario Bros 3.