Nintendo of America followed a strict set of rules during their early years, so that they wouldn't end up like the industry disaster Atari. One of these rules was that they would never repackage a game, like Atari had done with many of its titles. Since this game, the Japanese "Super Mario Bros. 2", was felt not to be sufficiently different from the first game and too difficult, it was never considered for a release in the USA. A Famicom game called Yume Koujou: Doki Doki Panic (1987) was used instead, which was reworked to make it look like a Super Mario game, and released internationally as Super Mario Bros. 2 (1988). The Japanese "Super Mario Bros. 2" was eventually released internationally in 1991, as the "Lost Levels" segment of Super Mario All-Stars (1993), but made somewhat easier.
In the game's "Lost Levels" version for the SNES game Super Mario All-Stars (1993) and the game's reappearance in Super Mario Bros. Deluxe (1999) for the Game Boy Color, the Poison Mushrooms are purple with skulls on them, in clear contrast to the regular mushrooms, which are orange with red spots. In the Japanese version, however, they are brown with black spots, making the two mushrooms look fairly similar.
At the end of World 9-4, the blocks form a word in Japanese. Romanized, this word reads as "Arigatou!", which translates into English as "Thanks!".
This game allows players to choose what playable character to play as per level, unlike the previous game where you're Mario (player 1) or Luigi (player 2) by default. Luigi jumps higher than Mario, but has lesser traction, and will slide as if he is on ice.
There is some debate about the story that Nintendo of America (NoA) passed on the game's release in the USA because they considered it too difficult for American players; some say that this was simply a rumor spread in 1993 to boost sales for Super Mario All-Stars (1993), a compilation for the SNES that included this game under the name "The Lost Levels". However, the difficulty was an actual concern: the game was genuinely made challenging for Mario fans, and a Japanese commercial even marketed it as such (showing players failing and screaming at the game in frustration). Nintendo consultant Howard Phillips had tested it for its suitability for the American market, and was quoted as saying: "As I continued to play, I found that [the game] asked me again and again to take a leap of faith, and that each of those leaps resulted in my immediate death. This was not a fun game to play. It was punishment - undeserved punishment. I put down my controller, astonished that [creator Shigeru Miyamoto] had chosen to design such a painful game." Phillips shared his thoughts with NoA's president, who agreed that releasing the game would be an unwise marketing decision: still recovering from a console recession, Nintendo was in dire need of a Mario sequel to establish a flagship franchise and consolidate its position amidst stiff competition from other consoles. However, since this game looked almost exactly like its predecessor Super Mario Bros. (1985), and the conversion from the Japanese Famicon system to the NES would take time, there was fear that it would look outdated upon release, and its difficulty would further alienate fans. Hence NoA's request to Japan to create a different sequel for the American market, which became Super Mario Bros. 2 (1988).