Yume Kōjō: Doki Doki Panic

Yume Kojo: Doki Doki Panic (夢工場 ドキドキパニック Yume Kōjō: Doki Doki Panikku: noting that "doki doki" is a Japanese onomatopoeia for a rapidly beating heart, this is often translated as "Dream Factory: Heart-Pounding Panic") is a Japan-only video game developed by Nintendo in cooperation with Fuji Television for the Famicom Disk System.

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 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.

Impact on the Mario Series
Shigeru Miyamoto was more involved with the development of Doki Doki Panic than he was in the Japanese Super Mario Bros. 2. Many of the game's enemies have become generic Mario enemies, though they were not intended to be that at the time of their creation. This includes Shy Guys, Birdos, Pokeys, and many more. Of particular note is how Mario, Luigi, Toad, and Princess Toadstool's skills and attacks have been shaped by the skills of the characters they replaced.

Interestingly, Mario elements had already been in place prior to the overhaul for America - both POW Blocks (from Mario Bros.) and Starmen (from Super Mario Bros.) are frequent, and powerful, items that serve the same purposes as their games of origin.

Differences Between Games
Several changes were made in order to make the game appropriate for the Mario series. Graphical changes were made for certain enemies and characters. Additionally, the albino Mouser boss, perceived as too difficult for American gamers, was replaced with the Clawgrip boss. 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 advanced for European and American gamers.

Characters (and their American counterparts)

 * Imajin, the balanced character, is the perfect fit for a player just starting out. While Mario replaced him, Imajin's balance in all areas has since become a staple of Mario's in the sports games.
 * Mama, with the ability to jump higher and lightly hover at the top of her jumps, is a good choice for areas with long gaps. Luigi took her stead, possibly because he had already been given higher jumps than Mario in Super Mario Bros.: The Lost Levels. Like his brother's balanced stats, Luigi's higher jumps has become a mainstay in the Mario series.
 * Lina, the perfect character for a player with trouble timing jumps, could hover, although she is lackluster in speed and strength. Princess Toadstool replaced her. Lina's moves inspired two of Peach's moves in Super Smash Bros. Melee and later Super Smash Bros. Brawl.
 * Papa, the strongest character in the game, could throw enemies and items very far, but he is not very good at running or jumping. While Toad takes his stead, in future video games (other than Wario's Woods and Mario Superstar Baseball) Toad was not endowed with the Papa's might.

Miscellaneous

 * The title screen is entirely different.
 * Rather than the storyline taking place in a dream world, it takes place within a storybook. Also, the storyline was about two kids who were reading a book, and ended up getting themselves kidnapped by Wart, which reached his hand from the book and pulled them in.
 * A save feature is included.
 * The player cannot run by holding the B button, as that's a feature that was exclusive to the Mario series.
 * There were slight music and graphical changes.
 * It takes fewer hits for Wart to be defeated in Doki Doki Panic than it does in Super Mario Bros. 2.
 * The waterfall goes faster than in Super Mario Bros 2.
 * Sound effects were changed due to limitations between the Famicom Disk System and the NES, which had less pin connectors.