Clouds and bushes use the same sprites, but alternate palettes.

The Bowsers in the castles of Worlds 1 through 7 are actually common enemies disguised as him. You can reveal the disguises by killing the False Bowser with fireballs.

Super Mario Bros. was originally planned to be a shooting game. According to Shigeru Miyamoto, Mario's fireballs were going to be bullets, and he could fly on a cloud shooting at enemies.

The Minus World glitch is believed to be first acknowledged by Nintendo in the third issue of Nintendo Power (November/December, 1988, page 55).

During the development of Super Mario Bros., a 16x32 pixel square represented the player character. After asking to see sales figures from the head of Nintendo's Sales and Marketing Division, Takashi Tezuka and Shigeru Miyamoto decided to make Mario the game's protagonist due to the success of the Famicom port of Mario Bros.

According to Super Mario Bros. Wonder's art director Masanobu Sato, Shigeru Miyamoto reportedly explained during the development of the first Super Mario Bros. that the reason why Goombas damage Mario when walking into them is because they bite Mario on impact. Due to graphical and hardware limitations, this could not be shown at the time. However, while Super Mario Bros. Wonder is thought to be the first game in the mainline series that shows this detail in gameplay, it's not the first game in the overall franchise to show it, as Goombas had been seen biting in earlier spin-off games like Super Mario RPG: Legend of the Seven Stars.

According to source code leaked in 2020, during development of Super Mario Bros., Bowser was called "Big tortoice" [sic]

Super Mario Bros. / Duck Hunt / World Class Track Meet has unused graphics from Super Mario Bros: The Lost Levels, which can be activated by a Game Genie code, allowing one to play SMB1 levels with The Lost Levels graphics, albeit with some glitched tiles in different parts of the game.