Super Mario Bros. 3 is the first Platform Game to be able to scroll in every direction, including diagonally. Previous Platform Games were limited to straight up-and-down or straight left-to-right.
Author Phobia: Chain Chomps came from an experience Shigeru Miyamoto had as a child, when a dog chased after him as he approached but stopped just inches from him because the dog was tied to a stake.
Bad Export for You: Because the e-Reader flopped in North America, half of the Super Mario Advance 4 cards never made it out of Japan, which left "World-e" incomplete with only one of the mini-game houses open and a rather empty e-Coin castle. All missing levels are available for the Wii UVirtual Console release, though.
No Export for You: North America and Australia didn't receive all of the Super Mario Advance 4 e-Reader levels until its Wii U Virtual Console release, and Europe didn't receive any of them until then.
According to Nintendo Power Volume 10, a power-up where Mario transformed into a centaur was planned.
The NES ROMs contain a bunch of unused and unfinished content, such as entire levels, enemy variants, miscellaneous graphics, different types of mini-games apparently hosted by friendly Koopa Troopas and Hammer Bros., and more.
In addition to the extra World-e content in the Japanese version of Super Mario Advance 4, a lot more had seemingly been planned, as evidenced by the large amounts of unused content on the ROM and the fact that the world's castle, which displays the e-coins located in each of the World-e levels, was originally planned to have three floors, each with a full length e-coin gallery.
Write Who You Know: Shigeru Miyamoto based the Boos' famous "shy when you're looking, mean when you're not" quirk on the wife of fellow developer Takashi Tezuka. Specifically, her frustration at him working long hours.