Dream World: Dokidoki Panic

Yume Kōjō: Doki Doki Panic, translated as Dream World: Dokidoki Panic or Dream Factory: Heart-Pounding Panic and usually referred to as simply Doki Doki Panic, is a Japan-only video game developed by Nintendo in cooperation with Fuji Television (who also made All Night Nippon Super Mario Bros.) for the Family Computer Disk System to promote its event called Yume Kōjō '87 (translates to Dream Factory '87). It was later released outside of Japan in an altered format under the name Super Mario Bros. 2, since the original Japanese Super Mario Bros. sequel, Super Mario Bros.: The Lost Levels, was deemed too similar to the original and too difficult for overseas players. Eventually, the altered Mario version of Doki Doki Panic was released in Japan as well, under the title Super Mario USA.

The game takes place inside a storybook. The book's story tells of the dream world of Muu, where the quality of dreams determined the quality of the weather the next day. Because of this, the Muu citizens invented a dream machine so they could always have good dreams. One day, a mischievous being named Mamu (whose name was changed to Wart for Super Mario Bros. 2) invaded the land and used the dream machine to make nightmarish monsters. However, the Muu people learned of his weakness to vegetables and used them to defeat him.

The old storybook had found its way into the hands of a pet monkey, Rūsa, who gives the book to the young twins Poki and Piki. However, the twins quarrel and end up ripping out the last page of the book, causing its ending to be erased. Mamu, freed, reaches through the pages and grabs the twins, pulling them into the book. Rūsa gets the twins' parents, Mama and Papa, their brother, Imajin, and Imajin's girlfriend, Lina, and they enter the book to rescue them.

Several changes were made in order to make the game appropriate for the Super Mario franchise. Graphical changes were made for certain enemies and characters. Additionally, the cream white Mouser boss featured in World 5-3 was replaced with Clawgrip. This change was in tune with the decision to release the edited Doki Doki Panic in place of the Japanese Super Mario Bros. 2, which Nintendo of Japan feared was too hard for European and American gamers.