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. Even worse in Europe where the e-Reader never got released at all, so no e-Reader levels can be played with normal means on European versions, even if everything is indeed present and translated. All missing levels were later made available for the Wii UVirtual Console release and the Nintendo Switch Online Expansion Pack.
There are fifteen (mostly) incomplete levels hiding in the coding.
Worlds 4-5 and 5-1 have dummied-out exits. The latter is the result of localization. A glitch in the Famicom version, involving the original exit, led to other versions having an alternate exit for this level, although the first one was never taken out.
There are even two dummied-out enemies: gold Cheep Cheeps and green Para-Beetles, both of which move faster than their red brethren.
All the e-Reader content is present and translated in every version of Advance, but the content is inaccessible to varying degrees depending on the region. Two whole sets of e-Reader cards didn't make it to North America, while the European and Australian releases didn't get any of the cards due to the peripheral skipping out on those markets. This was rectified with the Wii UVirtual Console and Nintendo Switch Online Expansion release, which also has all the e-Reader levels unlocked in all regions.
Early-Bird Release: This game was first released in the United States in 1989 as a Playchoice-10 arcade cabinet, roughly six months before its home release.
First Appearance: This game introduces the Koopalings, Bowser's most loyal minions (and may or may not be his children). Enemies like Boos, Thwomps, Dry Bones and Chain Chomps debut here as well.
Kids' Meal Toy: This game had a Happy Meal tie-in from McDonald's in 1990. The four toys consisted of a springy Mario, a pull-back Luigi, a somersaulting Goomba, and a hopping Koopa Paratroopa with a finger pump.
The international release of the game was delayed by over a year due to a ROM chip shortage affecting the entire electronics industry as well Nintendo wanting more breathing room between Mario games, since they had released Super Mario Bros. 2 outside of Japan in 1988 (shortly before Mario 3's Japanese release), and the first handheld game in the series (Super Mario Land) was on the way as well. Nintendo took advantage of the extra wait to advertise the game overseas with The Wizard. This was even more pronounced in Europe, where it was actually released afterSonic the Hedgehog.
Half of the World-e levels wouldn't leave Japan until the Wii U Virtual Console re-release, finally giving Americans and Europeans the full World-e experience.
In Turning Red, at the end of the film when Mei meets up with her friends, she transforms her ears and tail, resembling the raccoon power up from Super Mario Bros. 3, which also appears earlier where she changes her hands to paws as well and during their money hustle, where they sell fake ears and tails as merchandise.
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.
id Software created a demo as proof-of concept for their proposed DOS port of the game. While Nintendo of Japan was impressed, they declined as they had no interest in releasing games outside of their own platform. Id instead used the technology to create Commander Keen.
McDonald's had a Happy Meal tie-in featuring four toys. The final product featured toys of Mario, Luigi, a Goomba, and a Koopa Paratroopa. Concept art reveals that a fifth toy that was planned would have been the King Koopa Fireball Blaster. This toy would have been a figure of King Koopa that could shoot a plastic fireball when a button was pressed. While the toy went unproduced, its concept was revisited with later Bowser Happy Meal toys in 2017 and 2023.
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.
This also applies to Miyamoto's inspiration for Chain Chomps, coming from a fearful childhood memory of a dog chasing him but being held back by a stake it was tied to.
Other trivia:
Super Mario Bros. 3 is the first Platform Game on the NES to be able to scroll in every direction, including diagonally. Previous NES platformers were limited to straight up-and-down or straight left-to-right.note Nintendo actually had to get creative with their own hardware with this as the NES did not natively support diagonal scrolling or even multiple scrolling modes at once. Nintendo would essentially put the system into vertical scrolling mode to allow vertical camera movement and update the name table (the part of memory that stores the tiles as arranged to be displayed on screen) on the fly as Mario moves left and right to simultaneously enable horizontal camera movement, which is the reason why there is some weird artifacting to the right of the screen, but the result is a camera system that can follow Mario in any direction.
Super Mario Bros. 2, minus the second half with a faster beat.