What peripheral was bundled with Donkey Kong 64 in many regions?

The peripheral bundled with Donkey Kong 64 in many regions was the Expansion Pak.

Donkey Kong 64 was released for the Nintendo 64 in 1999 and required the Expansion Pak, which added 4 MB of RAM to the console. That extra memory doubled the system’s total RAM from 4 MB to 8 MB and helped the game handle its large 3D environments, multiple playable characters, and numerous collectibles.

Nintendo sold special Donkey Kong 64 bundles containing the game, a banana-yellow cartridge, a translucent green Nintendo 64 console, and the required Expansion Pak. This is why the accessory is strongly associated with the game, although regional packaging and bundle availability varied.

The other options are different Nintendo 64 accessories. A Controller Pak stored save data, a Transfer Pak connected certain N64 games with Game Boy cartridges, and a Rumble Pak added vibration. Donkey Kong 64’s distinctive memory requirement is the key clue.