World 4-1 (Super Mario Bros.) - Super Mario Wiki, the Mario encyclopedia

World 4-1 is the first level of World 4 in Super Mario Bros. and the thirteenth level overall in said game. This level introduces the Lakitu and Spiny enemies in the series.

World 4 (Yoshi's Island DS), MarioWiki

Super Mario Bros. 4 Level I: World 1-1 by stephen718 on DeviantArt

World 1-1 (Super Mario Bros. 2) - Super Mario Wiki, the Mario encyclopedia

World 1-1 (Super Mario 3D Land), MarioWiki

World 4-Castle (New Super Mario Bros. 2) - Super Mario Wiki, the Mario encyclopedia

World 4-5 (New Super Mario Bros.) - Super Mario Wiki, the Mario encyclopedia

Super Mario 3D World, Nintendo

World 2-2 (Super Mario Bros.) - Super Mario Wiki, the Mario encyclopedia

World 1-4 (Super Mario Bros. 3) - Super Mario Wiki, the Mario encyclopedia

World 8-4 (Super Mario Bros.: The Lost Levels) - Super Mario Wiki, the Mario encyclopedia

World 4-1 (New Super Mario Bros. Wii), MarioWiki

World 1-Fortress - Super Mario Wiki, the Mario encyclopedia

World 4-1 (Super Mario Bros.) - Super Mario Wiki, the Mario encyclopedia