World 1 (Super Mario Bros. 2)

World 1 is the first world Mario, Luigi, Peach, and Toad venture through in Super Mario Bros. 2. It is divided into three levels and inhabited by Tweeters, Shy Guys, Snifits, and Pidgits. At the ends of the first two levels, the heroes have to face the egg-spitting Birdo, and Mouser at the end of the last level. It tends to have waterfalls with log bridges.

Trivia

 * In the Game Boy Advance version, World 1-1 got the most changes of all the levels in World 1.