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 to promote its event called Yume Kojō '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 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.

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 cream white Mouser boss 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 advanced for European and American gamers.

Characters (and their Mario counterparts)

 * Imajin is the balanced character. While Mario replaces him, Imajin's balance in all areas has since become a staple of Mario's in certain games.
 * Mama has the ability to jump higher and lightly hover at the top of her jumps. Luigi takes her place as he had already had higher jumps than Mario in Super Mario Bros.: The Lost Levels. Like his brother's balanced stats, Luigi's higher jumps has stayed in the Mario series.
 * Lina can hover, although she is low in speed and strength. Princess Toadstool replaces her. Lina's moves inspired two of Toadstool's moves in Super Smash Bros. Melee and later Super Smash Bros. Brawl, Toadstool being able to float is often used or seen in later games, including Super Mario 3D World.
 * Papa, the strongest character in the game, can 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 rarely has Papa's stats.

Graphics

 * Shells were originally Blackface heads. They were edited in the western releases due to the controversy over blackface mocking African-Americans.
 * Magic Potions were originally Magic Lamps, though they both functioned the same way.
 * Grass tufts were black instead of red.
 * Mask Gates were originally large masks.
 * The explosion icon says "BOM" in Doki Doki Panic, and "BOMB" in Super Mario Bros. 2.
 * Phantos were less menacing originally.
 * Mushroom Blocks were originally various masks.
 * Vegetables looked slightly different.
 * In the US version, animations are given to Cherries, POW Blocks, vines, grass tufts, Crystal Balls, Bomb fuses, water, cloud platforms, and spikes.
 * Waterfalls move much faster.

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 named Poki and Piki 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 monkey known as Rūsa witnessed this and informed the Arabian family.
 * 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 graphic changes.
 * It takes fewer hits for Wart to be defeated in Doki Doki Panic than it does in Super Mario Bros. 2. This is also present in the prototype version of 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
 * After leaving a Key's home room, a Phanto inexplicably begins assaulting the player out of nowhere. In Super Mario Bros. 2, the Phanto now appears, albeit stationary and (seemingly) harmless, in the Key's home room. However, once they Key is retrieved, the Phanto comes to life and begins attacking.
 * 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.''
 * The highest cloud platform in a section of 7-1 was removed, and the gray Snifit was moved onto a pillar where the cloud was once attached to.
 * Imajin, Lina, Papa, and Mama do not shrink when they have one hit point left.
 * The Subspace music for Super Mario Bros. 2 is the overworld theme for Super Mario Bros., while the music for Doki Doki Panic is an Arabian theme.
 * The musical score for the overworld theme is slightly shorter. The extended theme is exclusive to Super Mario Bros 2.
 * Enemies scream when defeated.
 * Upon grabbing the Starman, an Arabian-sounding tune plays in Doki Doki Panic, while the standard Super Mario Bros. Starman fanfare plays in SMB2.

References in later games

 * Wario Land II - A Big Face (revised as a Turtle Shell in Super Mario Bros. 2) can be found as a treasure in Chapter 3, Story 4: Escape from Maze Woods.
 * Mario Kart 8: On Toad Harbor, there is a sign saying "Shy Guy Metals: Since 1987", while this game was the debut of Shy Guys, and it was released in 1987.
 * Super Smash Bros. for Wii U - Several trophies mention that a character or enemy actually debuted in Doki Doki Panic (removing the Yume Kojō part of the title, presumably due to licensing concerns).

Trivia

 * The coin counter in Bonus Chance segments is displayed in hexadecimal. When the player gets more than nine coins in a level, letters from A to F are used instead.
 * Imajin, Lina, Mama, Papa, Poki and Piki, and Rusa were created by the Fuji Television Network as the mascots for their Yume Kojō '87 (夢工場 '87) event, while all the other characters in the game were created by Nintendo.
 * Apparently, the masks in the game are a direct reference to said event. The event's theme was based around a Mardi Gras celebration.
 * Despite appearing in the manual, no Gray Shy Guys appear in the game.