Yume Kōjō: Doki Doki Panic

Yume Kōjō: Doki Doki Panic (translated as "Dream Factory: Heart-Pounding Panic") is a Japan-only video game developed by Nintendo in cooperation with Fuji Television for the Family Computer 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 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.

Story
The game takes place inside a book. The book's story tells of the land of Mu, where the quality of dreams determined the quality of the weather the next day. Because of this, the Mu citizens invented a dream machine so they could always have good dreams. One day, an evil toad named Mamu (whose name was changed to Wart for Super Mario Bros. 2) invaded the land and twisted the dream machine into a nightmare machine. However, the Mu people learned of his weakness to vegetables, and used them to defeat him.

The book had found its way into an Arabian family. Their pet monkey, Rusa, gives the book to 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. Rusa gets the twins' parents, Mama and Papa, their brother, Imajin, and Imajin's girlfriend, Lina, and they enter the book to rescue them.

Impact on the Mario Series
The Doki Doki Panic engine started as a Mario-style tech demo using vertical-scrolling mechanics as opposed to side-scrolling mechanics. Shigeru Miyamoto suggested the inclusion of side-scrolling mechanics to make it more of a Mario concept. Nintendo entered a licensing deal with Fuji Television, and the game's development proceeded with Yume Kōjō characters. Shigeru Miyamoto as a result was more involved with the development of Doki Doki Panic than he was in what eventually became the original Super Mario Bros. 2. Many of the game's enemies have become generic Mario enemies, though many 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 hard 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. However, Luigi can jump slightly higher than Mama. Like his brother's balanced stats, his 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 Peach's moves in the Super Smash Bros series, and Peach being able to float is often used or seen in later games, including Super Mario 3D World.
 * Papa is the strongest character in the game and can run the fastest, but he is not very good at 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. However, Toad regains these properties in Super Mario 3D World, where he is the fastest character and a poor jumper.
 * Poki and Piki are non-playable characters who get captured by Wart at the beginning of the game, and are rescued after his defeat. They are replaced by the Subcons in Super Mario Bros. 2, which are also present in Doki Doki Panic's endings.

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.
 * Mushrooms were originally large hearts.
 * 1-Up Mushrooms were originally the heads of the character being controlled
 * Grass tufts were black instead of red.
 * Mask Gates were originally generic masks instead of hawk 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.
 * Some 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.
 * The title screen music is the credits theme from Super Mario Bros. 2, but without the sampling from the Super Mario Bros. overworld theme.
 * Rather than the storyline taking place in a dream world, it takes place within a storybook. The plot of the game is about two kids named Poki and Piki who fought over reading a book, and ended up getting themselves pulled in by Wart after accidentally tearing out the last page. 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 franchise.
 * It takes four hits for Wart to be defeated in Doki Doki Panic, two less than 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 Disk System and the NES, which had fewer pin connectors.
 * 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 version of Mouser appeared as the boss of 5-3. In the localized versions, he was replaced with Clawgrip. his replacement was likely because albino Mouser attacked much more erratically than his grey-skinned counterparts, thus making him seem too powerful. Because of this, Clawgrip is the only boss 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 characters and artwork are based on an Arabian style theme.
 * 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 player select and overworld themes are slightly shorter. The extended rhythms are 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.
 * The player must beat the game with all four characters to view the ending in Doki Doki Panic, unlike Super Mario Bros. 2, where the player only needs to beat the game once to view the ending.
 * The shortcut in 6-3 is slightly different: in Doki Doki Panic, one can simply jump down from the cloud platform with the door, however in Super Mario Bros. 2 two more cloud platforms stand between the door and ground.

References in later games

 * Super Mario Bros. 2: Yume Kōjō: Doki Doki Panic is the source of Super Mario Bros. 2, and few differences exist between the games. In addition, Doki Doki Panics cover art was traced and edited into a piece of official art for Super Mario Bros. 2. The credits theme from Super Mario Bros. 2, which replaced a completely different song from Doki Doki Panic, is remixed from an arpeggiated chord progression and melody taken from Doki Doki Panics title screen / intro theme, a song which likewise does not exist in Super Mario Bros. 2.
 * 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 Mario 3D World: The player being required to beat all levels with all characters (Mario, Luigi, Toad, Princess Peach, and Rosalina), barring the Captain Toad levels, to unlock all related stamps as well as all five profile stars was most likely a reference to how the player was required to beat all levels with all characters (Imajin, Mama, Papa, and Lina).
 * Super Smash Bros. for Wii U: The trophies for Birdo and Shy Guy mention that they actually debuted in Doki Doki Panic (removing the Yume Kojō part of the title, presumably due to licensing concerns).
 * Paper Mario: Color Splash: At the concert in Plum Park, Birdo sings about "a Doki Doki Panic" and egg spit on people's faces, referencing her first appearance in this game.

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.
 * Despite appearing in the manual, no Gray Shy Guys appear in the game.
 * Coincidentally, some artwork and commercials of the game feature Imajin and Lina posing with Mario and Princess Peach, their eventual replacements in Super Mario Bros. 2.