Yume Kōjō: Doki Doki Panic

Yume Kōjō: 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, Bob-ombs, and numerous others. 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, some 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 in 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 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 is the balanced character. While Mario replaced him, Imajin's balance in all areas has since become a staple of Mario's in the sports games.
 * Mama has the ability to jump higher and lightly hover at the top of her jumps. Luigi took her place, 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 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 place, in future video games (other than indirect references in 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 plot of the game is about two kids who are reading a book, and ended up getting themselves kidnapped by Wart, who reached his hand from the book and pulled them in.
 * A save feature is included.
 * The player cannot run by holding the button, as that was a feature that was exclusive to the Mario series.
 * There are 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 are changed due to limitations between the Famicom Disk System and the NES, which had fewer pin connectors.
 * Many items are unanimated, such as the turnips or the POW Block
 * Hearts are used to enhance hit points rather than Mushrooms
 * Phantos chases the character after the character leaves the area with the key. In SMB2, Phantos come to life upon touching the key.
 * An albino Mouser appeared as the boss of 5-3. In the localized versions, it was replaced with Clawgrip. Its replacement was likely because the albino Mouser attacked much more erratically than its grey-skinned counterparts, thus making it seem too powerful. Because of this, Clawgrip is the only enemy exclusive to the western releases.
 * Imajin, Lina, Papa, and Mama do not shrink when they have one hit point left.

Trivia

 * When the player gets more than nine coins in a level, the bonus at the end will mark the number with letters, starting with A.