World 2-Castle (New Super Mario Bros. Wii)
This is an autoscrolling castle level filled with lava pits, and three-way corridors, of which only one is the correct path, much like in Super Mario Bros. and Super Mario Bros.: The Lost Levels. If the correct path is taken, a chime indicating so sounds and the player will go to the next part; if it is incorrect, a buzzer sounds and the player will have to repeat the same area all over again. In order to complete that area quickly, the player needs to take the upper route, the lower route, and the center route in that exact order. Lava Bubbles are also common in this castle. If Mario or any of the other players stay too long between a wall and the edge of the screen, the autoscrolling level squishes them, instantly killing them and causing them to lose a life.
Roy Koopa is fought here for the second time. He attacks by popping out of pipes that Magikoopa produces with his magic before the start of the battle. When Roy jumps out of a pipe, he causes a tremor upon landing, which temporarily stuns any players on the ground. Mario also needs to avoid getting squished by Roy. Roy is defeated after getting hit three times. Upon his defeat, the player gets the key to unlock World 3.