id software sent a PC demo of Super Mario Bros. 3 to Nintendo hoping to gain authorization to make an official port. Nintendo was impressed but declined, deciding to stick to their own platforms. The demo was based on a test they named 'Dangerous Dave in "Copyright Infringement"', which was a playable recreation of World 1-1 with Mario's sprite replaced by John Romero's Dangerous Dave character.

The three islands on World 7 (Pipe Land) are actually shaped like the Overworld Pipe sprites.

The sound of the warp whistle which is based on the recorder from the original Legend of Zelda, can be heard in the title screen theme of The Legend of Zelda: Ocarina of Time.

The Water Land theme was later used as the theme for the Fairy Fountain in the Legend of Zelda series.

For every 80,000 points you score, a matching card game will appear on the board. This is a chance to receive items such as coins and power-ups. There are only a total of Eight (8) different patterns.

Several of the Koopa Kids' names are parodies of various musical celebrities, most of whom were popular at the time of SMB3's production.

- Iggy Koopa is named after American rock singer Iggy Pop.
- Lemmy Koopa takes his name from Lemmy Kilmister, a British heavy metal artist best known from his work in the band Motörhead.
- Ludwig Von Koopa is named after 19th Century 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 KISS.
- Roy Koopa is named after Roy Orbison, and both wear horn-rimmed sunglasses.
- Wendy O. Koopa is named after Wendy O. Williams, an American punk singer.

It's unclear who Larry Koopa is supposed to be based on, but he could be based on Larry Mullen Jr, the drummer for the band U2.

The fortress in World 1 was slightly changed from the Japanese version to make things a bit easier. The right wall in the spike hallway was originally farther away, and the door was under a spike.

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

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.

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 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.

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