Platform: Nintendo 3DS

In 2021, dataminers discovered a consistent security vulnerability, later termed "ENLBufferPwn", in multiple Nintendo 3DS, Wii U, and Nintendo Switch games. ENLBufferPwn made it possible to inject code into another player's system during online multiplayer by deliberately triggering a buffer overflow in a game's "ENL" network library. The glitch was known to be possible in Animal Crossing: New Horizons, Arms, Mario Kart 7 (where the glitch instead targets the "Net" library), Mario Kart 8, Mario Kart 8 Deluxe, Nintendo Switch Sports, Splatoon, Splatoon 2, Splatoon 3, and Super Mario Maker 2, with other games potentially being affected.

ENLBufferPwn generated significant cybersecurity concerns due to its ease of execution, the fact that it could be pulled off without the target player's notice, and the wide range of actions that could occur through it, up to and including identity theft and espionage. Reflecting this, the United States federal government's National Vulnerability Database gave the glitch a 9.8 rating, reflecting critical threats to public safety. Following multiple reports issued by white hat hackers between 2021 and 2022, Nintendo patched all known affected games to remove the vulnerabilities that made ENLBufferPwn possible.

When run on a Nintendo DSi or Nintendo 3DS, Action Replay DSi's icon and title will be listed as Game & Watch Collection. This is a way of working around the DSi's bootleg game protection, which is done by having a built-in whitelist of every official DS game, which Action Replay circumvents by tricking the device into thinking Game & Watch Collection is being played. Action Replay DSi contains almost every byte of data from Game & Watch Collection, but jumbled into an unplayable format.

According to video Game developer Yukio Futatsugi, his tabletop board game Machi Koro was originally going to be a digital board game available on the 3DS, but Nintendo encouraged Futatsugi and his company Grounding to go physical with it instead.

"My company has made a lot of board games, and Nintendo has told me that our games are interesting. Machikoro was supposed to be on 3DS, but the idea didn’t become a reality because it wouldn’t sell on 3DS, and so Nintendo suggested, 'Hey, Grounding, why don’t you manufacture this as a physical board game, I’m sure it will sell really well!' and that’s how Grounding came to become a board game creator."

In the Japanese and American versions of the 3DS' "StreetPass Mii Plaza", when attempting to purchase a DLC from a rabbit but then declining to buy it will cause the rabbit to depressively say "Oh, I see...". However, the European version removed the rabbit's depressed response and replaced it with a more neutral "Fair enough!", instead.

This was done to bring it in line with European laws put in place to prevent manipulating children into purchases; "Games should not include practices that are aggressive, or which otherwise have the potential to exploit a child's inherent inexperience, vulnerability or credulity or to place undue influence or pressure on a child to make a purchase."

Holding the start + select buttons while booting an original Nintendo DS cartridge will load the game in its native resolution, rather than stretching it.

In 2012 the Louvre museum in Paris, France, started offering 3DS museum guides. The purchase of the hardware was sponsored by Korean Air, and all the museum guides are branded with the airline's logo.

Placing the AR Card on a colored surface during the AR Free Fishing game (available from the AR Arcade for 1 Play Coin) yields different effects based on the color. For instance, a blue background will display sardines, a green one will show green Koopa shells, and the red contains jumping Cheep Cheeps.

Making noise into the microphone while on the system settings screen will cause the icons to spin around the wrench. While doing this, the wifi helper icon can be seen on the back of the internet icon.

In the 3DS Sound app, when playing a sound file, switching to the Game & Watch Soccer background and pressing any button will allow you to take control and play the game.

If you blow into the mic while highlighting a 3DS application, the icon will spin around faster.