Donut Plains 2
Donut Plains 2 is an underground level of the Donut Plains area. The level autoscrolls and has some underground enemies such as Buzzy Beetles and Swoopers. There are three exits in the level. While beating Donut Plains 2 is not compulsory for finishing the game, it is the only way to get to the Green Switch Palace.
The level starts of with Mario or Luigi out of a pipe. After that, the screen starts to scroll. Now, the player have to maneuver around moving yellow platforms, a few Buzzy Beetles and Swoopers. After that, the player eventually encounters a few Warp Pipes. After going forward a little more, Mario or Luigi encounters the gate and finish the level.
The other two exits are in the room after Mario or Luigi enters the Warp Pipe as mentioned below.
While there are virtually no hidden rooms or special areas in Donut Plains 2, the level has three exits, two of which open the regular way to the Donut Ghost House in the north-east of Donut Plains 2.
Right after the first green ! Block (which is a green Dotted Line Block instead if the green ! Switch has not been activated yet), there is a green upside-down Warp Pipe. The player may ignore this pipe and head right. This can be considered the standard way, as it's the only way to get all the Dragon Coins in the level. Finally, Mario reaches the Giant Gate and continue to the Donut Ghost House.
Another way that leads to the Ghost House is to enter the Warp Pipe mentioned above. Mario enters a special room with a Chargin' Chuck kicking footballs at him. The auto-scrolling also stops. At the end of the room, there is a Warp Pipe leading to the Giant Gate.
With this exit, Mario is able to reach the Green Switch Palace. This, however, requires to have either Yoshi, a Shell or a Cape. First, Mario has to enter the special room like above. Yoshi may eat the Blue Shell at the end of the room, which gives him the ability to fly. He can fly up where the Turning Blocks are, and pass through a narrow gap where the player will find Key and Keyhole. The Key can also be reached by flying through it as Cape Mario or Luigi. Additionally, the uppermost Turning Block releases a Beanstalk when hit, which makes passing through the gap easier. Alternatively, this Block can be hit with the Shell. The player can use the other three Turning Blocks as stairs to get to the vine, or he can simply fly up. When the player puts the Key into the hole, a new way westwards opens which takes him or her to the Green Switch Palace.