Before there was a Super Mario Bros. 2 (in the US), and before there was a Doki Doki Panic, Nintendo was messing around with the idea of vertical platforming. "The idea was that you would have people vertically ascending, and you would have items and blocks that you could pile up to go higher, or you could grab your friend that you were playing with and throw them to try and continue to ascend," Donkey Kong Country Returns producer and Super Mario Bros. 2 director Kensuke Tanabe, who worked on the prototype, told Game|Life. "The game was mocked up (so that) when the player climbed about two-thirds of the way up the screen, it would scroll so that the player was pushed further down."

The technology was cool, but there was a problem: the prototype wasn't actually any fun. Shigeru Miyamoto suggested adding some more traditional Mario-style side-scrolling, and the weird concept that eventually became Mario 2 began to take shape. "Picking up blocks was the same thing as pulling out vegetables from the ground," Tanabe said. This concept was first released as Yume Kojo: Doki Doki Panic; while it was in development, Fuji Television made a deal with Nintendo to release a game featuring characters for the Yume Kojo technology expo.

Then when it was converted from Famicom Disk System format to a cartridge for Western release, Nintendo took the chance to make a couple of other changes -- like putting the Mario characters in. "We knew these Fuji TV characters wouldn't be popular in America," Tanabe said, "but what would be attractive in America would be the Mario characters."