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.

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

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.

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.

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

The current world record for fastest time beating the game is 4:54.631 seconds by speed runner Niftski as of September 8, 2023. This record surpassed his previous record by ~0.167 seconds.

Super Mario Bros. was originally planned to have an "air, land, and sea" concept. While the player normally runs on solid ground and swims underwater in certain levels, designer Takashi Tezuka explained in interviews that Mario would have been able to fight in the air while riding in a cloud. Instead of creating more brand new air-based enemies, they attached wings to an existing enemy to save on memory, resulting in the creation of the Koopa Paratroopa. However, the trial demo created to test these levels was deemed not fun to play, feeling more like a shoot 'em up game than what they were hoping. On top of this, the levels were deemed to be contributing to the memory constraints, leading to their removal. However, Tezuka strongly felt the game should still have air-based levels, leading him to suggest an idea to director Shigeru Miyamoto inspired by the fairy tale "Jack and the Beanstalk", where Mario could climb a vine from a Question Mark Block into the clouds, allowing players to collect coins in certain levels. Miyamoto liked the idea, and subsequently created the vines and constructed the game's bonus areas from existing elements. The "air, land, and sea" concept and Mario's ability to fight while in the air or clouds would be added in subsequent games in the series.

The South African release of Super Mario Bros. (included as a pack-in title for the Nintendo Entertainment System in the country) reuses its packaging from the European edition, with the only difference being its unique serial code, NES-SM-GPS. Notably, this is the only South African NES game which does this, as other releases there are explicitly marked for the region on the box art and cartridge label.

According to Pac-Man creator Toru Iwatani, Pac-Land had a strong influence on the development of Super Mario Bros. In an interview with Geek Culture, Iwatani stated:

There's an invisible 1-Up in the first level of each world, but whether or not it appears depends on whether or not you collected all the coins in the previous world's 3rd level. For instance, in World 3-1, to make the invisible 1-up that's on the bridge appear, you need to collect all the coins in World 2-3.

There are only two exceptions to this rule: World 1-1 because it's the very first level in the game, and World 2-1 where you're allowed to miss 2 coins in World 1-3. However, the hidden 1-Ups will always appear if you use a Warp Zone or the level select trick after beating the game. Another caveat is that each hidden 1-Up will only appear once so if you make the hidden 1-Up appear and lose a life, it won't reappear.

After losing all of your lives and returning to the title screen, holding A and then pressing Start will start you at the beginning of the last World you died on.

During a second playthrough Mario can obtain unlimited extra lives in World 1-2 through a glitch.
The player must start a 2 player game and Mario must die in World 1-2. As Luigi, the player must reach World 5-2 and die climbing the vine that comes out of a block next to a Hammer Bro.
When Mario re-starts World 1-2, the vine from World 5-2 will grow through the ground. Mario can can then climb the vine and come down between the Buzzy Beetles and earn 1-Ups.

The Power Up sound effect is very similar to the flagpole music just sped up around 20 times its usual speed.

The Spiny eggs are thrown by Lakitu in a simple way, with no horizontal movement whatsoever. However, this is not the intended behavior; it's actually the result of a bug! The eggs are supposed to be thrown out relative to the player's speed, Lakitu's speed, the player's position, and a pseudo-random value, as well as bounce off of any blocks or walls that they hit on the way down.

In the game's manual, it says that the Koopas use black magic.

Although Bloopers in Super Mario Bros. normally spawn only in water levels, they can be placed in non-water levels normally and will award a massive 1,000 points when stomped. Other "impossible" ways to kill enemies, such as hitting a Podoboo or Bowser with a Starman, only award the default 200 points. Given that Bloopers appear in non-water levels in Super Mario Bros.: The Lost Levels, and also award 1,000 points, this behavior was likely intended all along.

While a Goomba is the first enemy the player encounters, they were the last object added to Super Mario Bros. They were created after Miyamoto and his team decided that they needed an enemy that could be taken out with a single stomp, as opposed to the Koopa Troopas. Unfortunately, there was very little space left on the cartridge, and so it needed to be as small and simple as possible. They only used a single image, and made a walking animation by flipping it back and forth.

Super Mario Bros. was the first video game to receive an animated film adaptation. The film was called "Super Mario Bros.: Peach-Hime Kyushutsu Dai Sakusen!", and was only released in Japan in 1986. While the game would also be made into a poorly-received live-action film in 1993, it is not the first video game to receive a live-action film adaptation. The Mysterious Murasame Castle is one of the earliest known games to hold that title with a Japanese made-for-TV movie also in 1986.

In the game's manual, it's stated that the Koopas turned the Mushroom People into stone, bricks, and plants. This could imply that throughout the game you're killing the inhabitants of the Mushroom Kingdom.

It's possible to access an additional 256 worlds in the game through a glitch. There are two methods to access them via the Japanese Famicom version:
• Having a copy of both Super Mario Bros. and Tennis, first insert the Mario cartridge and then remove the game at the title screen whilst it's still on. Then insert the Tennis cartridge, and during a match, remove the game and place Super Mario Bros. back in. Reset the console and at the title screen hold down A and press Start.
• The second method involves the Family Basic cartridge and the keyboard peripheral. By inputting a series of code and then swapping the cartridge with Super Mario Bros., reset the console and then hold down A and press Start, which will grant players access to one of the 256 glitch worlds.

The Tennis method can also be done with the western version of Super Mario Bros. but only on the NES-101 model.

Each of the worlds appear to reuse assets from the other levels, resulting in various bugged stages. The Tennis game method is possible presumably due to both it and Super Mario Bros. using the same addresses, but don't place the same check values. Leaving the power on also retains the RAM and the previous check value remains.