
World 6 also shares a lot of similarities to Rock-Candy Mines from New Super Mario Bros. And, upon completing the Castles, Mario or Luigi skip an optional world, (World 3 skips World 4, and World 6 skips World 7), jump straight onto another world above (World 5 and World 8 respectively). Both worlds have a non-scrolling underwater level ( World 3-3 and World 6-5), before another level that introduces new enemies ( World 3-, which introduces Boo]s and Splunkins, and World 6-6, which introduces Chain Chomps) before going to the Castle, if taking the main path. For the first Tower and the Castle in World 6, said enemies and obstacles are swapped around.
In a strange parallel, the Tower and Castle in World 3 prominently featured Koopa Troopas, and Skewers with Dry Bones respectively. Additionally, there are two main levels and the unlockable level before the Tower. On both overworlds, the player can choose to start with either the first levels or an unlockable level. World 6 can be considered to be the mountain-themed counterpart to World 3. This airship level features Mechakoopas and has the first and only appearance of Rocky Wrenches and the Remote-Controlled Clown Car. In this level, there are spiked balls and Giant Spiked Balls that can hurt the player. The cannon will shoot straight to World 8. This level takes place in a dark underground cavern. It features Porcupuffers, tides and some large ? Blocks. This Fortress contains two giant Skewers on the floor and ceiling of the Fortress, they both collide in the middle of the Fort. Monty Moles are a common sight in this course.
In this level, there are Super Piranha Plants, Stalking Piranha Plants, and Buzzy Beetles. This is an underground level, with many rotating circular platforms, much like the ones in World 1. This level takes place on a series of high cliffs.