Super Mario 64 DS (Nintendo DS, 2004) includes an in-game feature that uses the console’s camera to scan specific QR codes to unlock features (notably the Yoshi camera/photo exchange and some promotional content). Below is a focused, practical guide covering what QR codes existed, how they were used, and how to replicate or use them today.
If you are looking for "QR codes" in the context of this game, you are likely looking for:
You can play the original DS cartridge on any 3DS system. While you can't "scan" the game into existence, you can use the Circle Pad for slightly smoother movement than the original D-pad allowed. The "Wario" Unlock
Reality: These are fictional stories designed for entertainment. Textures in the game that may look like QR codes to modern eyes are simply pixelated art from 2004 hardware limitations. 3. Modern Emulation and Homebrew