The Nintendo Entertainment System version of the game was released twice in English, and the worlds were renamed in the second version.

Desert Hill was changed to Desert World.
Ocean Side was changed to Water Land.
Big Island was changed to Giant Land.
The Sky was changed to Sky Land.
Iced Land was changed to Ice Land.
Pipe Maze was changed to Pipe Land.
Castle of Koopa was changed to Dark Land.

Grass Land kept its name.

In World 8, it's possible to bypass almost the entire battleship level by dropping into the water and swimming beneath the ship, jumping back on once the autoscroll reaches the vessel's stern. In the international version of the original NES release, one tile is removed from the rightmost portion of the ship in order to make the final jump easier.

If the player tries to make Mario slide while wearing a Hammer Suit, Mario will go into the suit's shell. However, if Mario obtains the Hammer Suit while sliding, an animation of Mario sliding while wearing the Hammer Suit is used. This is the only time this animation can ever be seen.

Over 30 new levels were created for the Game Boy Advance release of the game, Super Mario Advance 4: Super Mario Bros 3. In order to access these new levels, the player requires an e-Reader for Game Boy Advance and the various e-Reader Level Cards. To transfer the levels, the player would require 2 Game Boy Advance systems, the e-Reader, a link cable, and a copy of the game. Because of this, these levels have mostly fallen into obscurity.

Only 10 Level Cards were released in North America, while the other 20 Level Cards were released in Japan.

When the game was re-released on the Wii U Virtual Console and Nintendo Switch Online, all 38 e-Reader levels were unlocked by default as the e-Reader was only supported for the Game Boy Advance.

World 4 (Giant Land) is shaped like a Koopa Troopa.

Inside the game's data are two unused Mario sprites that looks almost identical to the final release, but his overalls are colored pink rather than blue.

If a Muncher is hit with Raccoon Mario's tail attack, it will turn into a block. This trick carried over to the Super Mario All-Stars version, but not the GBA version, Super Mario Advance 4: Super Mario Bros. 3.

Entering stage 5-3 with a Tanooki Suit and dropping into a Kuribo's Shoe while Statue Mario will grant the player total invincibility from enemies through the remainder of the level.

The king will give a different message than normal if Mario beats an airship wearing either the Frog Suit, the Tanooki Suit, or the Hammer Suit. The King will mistakenly believe that Mario has been transformed into a frog if he is wearing the Frog Suit, believe Mario is an actual raccoon if he's wearing the Tanooki Suit, and if Mario is wearing the Hammer Suit, he'll ask to borrow Mario's clothes.

In the SNES and GBA remakes of the game (Super Mario All-Stars and Super Mario Advance 4), the creatures the Mushroom kings were transformed into were changed from regular animals, such as a dog or a spider, to creatures specific to the Mario series that don't otherwise appear within Super Mario Bros. 3.

In the initial Japanese release, getting hit in any form other than Small Mario would revert Mario back to his small form. This was changed in the western release so that getting hit as Fire Mario or any of the suit power-ups reverted Mario back to Super Mario. This was carried on in every platformer Mario game released after Super Mario Bros. 3, with the exception of the original SNES release of Super Mario World.

If Boom Boom is defeated with a Starman, the "?" Orb that appears afterwards will spawn upside-down, and in the center of the arena.

The western version was slightly different compared to the Japanese release. The game was a bit easier, some levels and object placements were slightly altered, the speed of the credits was faster, as well as some other minor details.

As seen in early screenshots, Koopa Troopas and Hammer Bros. were going to host two mini-games. The minigames were a Question Block and a Dice Block game respectively, which also would have marked the first Mario game to have the Koopas standing instead of on all fours. These mini-games and their hosts seem to have been replaced by Toad.

If you let a Chain Chomp tug on its chain 49 times, it will actually break free.

Several of the Koopa Kids' names are parodies of various musical celebrities, most of whom were popular at the time of the game's production. The names were chosen by Nintendo of America employee Dayvv Brooks, a longtime music enthusiast who previously worked at music retailer Tower Records and as a radio DJ:

• Iggy Koopa is named after Iggy Pop, an American rock singer and frontman of the proto-punk group The Stooges.
• Lemmy Koopa takes his name from Lemmy Kilmister, a British heavy metal artist best known as the bassist and lead vocalist for the band Motörhead.
• Ludwig Von Koopa is named after 19th century German composer Ludwig van Beethoven, and shares his wild hairstyle.
• Morton Koopa Jr. is named after American pop and country singer Morton Downey Jr., now perhaps best known for his self-titled talk show. Morton Koopa Jr. also has a white face with a black star over his left eye, the trademark makeup of guitarist Paul Stanley from the American hard rock band KISS.
• Roy Koopa is named after American country singer Roy Orbison, and both wear horn-rimmed sunglasses.
• Wendy O. Koopa is named after Wendy O. Williams, an American punk singer and frontwoman of the shock rock band the Plasmatics.

The namesake of Larry Koopa remains unclear, with multiple explanations emerging over the years. In 2010, the web page for Nintendo's official UK magazine claimed that the character was named after American talk show host Larry King. However, two years later, Brooks himself made an edit on the Super Mario Wiki claiming that the name was actually derived from Larry Mullen Jr., the drummer for Irish pop rock band U2; site staffer Walkazo verified that the account was legitimate. Brooks ultimately denied both claims in a 2015 interview with Kotaku, stating that "There's no real-world equivalent — he's not Larry Mullen Jr. from U2 or Larry King — he just looked like a Larry."

The Koopalings were based on seven of the game's developers. They were all later named after musicians by the American localization team, as no distinct names were given in the Japanese version. It's also speculated the musical names were chosen because their scepters resemble microphones.

It was once planned for Mario to have a power up that turned him into a Centaur. This isn't as outlandish as it seems; the Tanooki suit was also inspired by the legendary Tanuki.

The box art for the game shows images from earlier stages of the game's development. The image of word 1 has different paths when compared to the final version, and the second image doesn't represent anything seen in the game's final build.

The island with the castle in World 3 resembles Japan, with the castle being the location of Kyoto, Nintendo's headquarters.