World 3, Split-path Sky is a bit interesting, in my opinion. The first level of this world, an auto-scrolling airship, has a secret exit. This secret exit takes you to a locked gate that requires a powerup you obtain from world 5. Upon taking this powerup to this gate, you can pass through and play through the other path of world 3 to reach world 6.
World 6, Snowy Snowlands, is inspired from the name Frosty Frost Frostlands in The Invasion 2.
World 7, Forest of Confusion, is a lot like SMW's Forest of Illusion, including a split path near the end. You can take either the mountain route, which is harder but straightforward, or the lake path, which is easier but more confusing.
World 8, Crazy Maze Cave, has a name that comes from Hazy Maze Cave in SM64, and is a large pipe maze. These pipes lead to islands bordering the main worlds in the overworld, with the level on each island themed after the world it is closest to. Most levels are completely optional, but you won't know which ones until you play them. Once you find the correct path and reach the end of the maze, a path forms linking the beginning and end of the world together so you don't have to remember the path every time you want to come through world 8.
World 9, Murderous Magma Land, is named after Lethal Lava Land from SM64, and is just what you'd expect from a lava world, other than being the 9th world instead of the 8th one.
World 10, Inferno Isles, consists of a few islands with 10 electronic themed castles on it. You can play these castles in any order, and each castle gives you part of a code which you input in a code level somewhere else to unlock world 11. The castles are clearly numbered so that you know which order each part of the code comes in.
World 11, Mt. Frostfire, is inspired by Hailfire Peaks from Banjo-Tooie, with the same general theme. Unlike that world however, fire and ice are right next to each other, instead of on other sides of the world. The constant threat of flames engulfing you coupled with the slippery ground of the ice is certainly something to be wary of. The hazards of both world types combine to make this a fittingly tough world.
World 12, Bowser's Challenge, is really just a level or two and Bowser's Castle. Did I mention that Bowser's Castle has about 10 levels in it? It's pretty big.
World 13, the star world, would normally be a bonus world. Not in this game! It's actually required. There are stars scattered throughout the game, most often in levels unlocked by secret exits. Collect enough and bring them to the star temple found off of the coast of Easy Isle to unlock the star world. There are also other bonuses you can unlock in there, such as a bunch of lives, Rent-A-Yoshi, and a secret room... It's main theme music is the Temporal Tower music from Pokémon Mystery Dungeon, so that's a thing.
World 14, the ztar world, is a bonus world that is very difficult. It's main theme music is the lavender town theme, also from Pokémon.
