The enemies of level 6-3 include Tweeters, Bob-ombs, Ninjis, and a few Hoopsters; the environment is cave, desert, and sky. Before battling the boss of World 6, the player must defeat a red Birdo with a Mushroom Block and Birdo Eggs. After Birdo is defeated, the player will enter a fight with Tryclyde (Mouser in the Game Boy Advance version of Super Mario Advance). This level is notable in that no key is found in the fortress, but this is because it was already used in 6-1.