From the Super Mario Wiki
Chocolate Island is a mountainous island located in the southeastern part of Dinosaur Land that serves as the sixth world in the game Super Mario World. The island is named after its chocolate-brown coloring, although upon activating Autumn mode, it will turn green instead (i.e. mint chocolate). Instead of lava, some levels have boiling hot mud (a reference to hot chocolate or hot cocoa). As levels are beaten, many of the small mountains covering the area are leveled to clear new paths across the island. This gradually gives the player access to more stages.
In Super Mario Kart there are two courses called Choco Island 1 and Choco Island 2 respectively, which appear based on Choco Island. Said courses return in Mario Kart: Super Circuit while Choco Island 2 appears in Mario Kart DS as a retro track.
Chocolate Island also serves as the basis of the desert level theme in Super Mario Maker 2, which features new music and has different semi-solid platforms than in Super Mario World. The night version of the theme has the course get hit by a sandstorm that blows left and right.
Except for Chocolate Secret, which is located underground near the Valley of Bowser and is accessible via Warp Pipe, all these levels are found on Chocolate Island. Levels that are marked with an asterisk (*) features another exit.
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