Dream Machine

The Dream Machine (also known as the Nightmare Machine) is a machine used by Wart prior to the events of the non-Mario game, Yume Kōjō: Doki Doki Panic, and the Mario version, Super Mario Bros. 2.

Yume Kōjō: Doki Doki Panic
In the tale of the world of dreams, Muu (known as Subcon in the Mario series), the Dream Machine was created by the Muu people to control the weather and sustain good dreams to all the inhabitants. One day, the mischievous Mamu (later renamed Wart) tampered with the Dream Machine to produce several monsters. The Muu people originally managed to stop Mamu on their own, but when the twins Piki and Poki accidentally ripped out the last page of the book, Mamu attempted to rewrite the ending and kidnapped them. At the final battle, the Dream Machine creates turnips, which the twins' family has to throw four times in Mamu's open mouth in order to defeat him.

Super Mario Bros. 2
In Super Mario Bros. 2, the Dream Machine plays an identical role, although its background as the prize of the peace-loving people is omitted from the story. It is still implied to create monsters that Wart then uses to increase the numbers of soldiers for the 8 bits and take control of Subcon. During the final battle, the Dream Machine shoots out vegetables, which are the only way to defeat Wart.

BS Super Mario USA
The Dream Machine made its return in the pseudo-sequel, BS Super Mario USA. It only makes an appearance in Wart's secret room in a vase from Subspace that is almost identical to that of the factory's final room. The Dream Machine is used for the same purpose it had in the first game.