There have been plenty of rare and elusive Nintendo consoles over the past few decades, either released as one-offs or under limited circumstances, and the 'McDonald's DS' is right up there as one of the more quirky system variants.
You might know about it already – McDonald's-branded Nintendo DS consoles were sent out to Japanese McDonald's branches back in 2010, only ever being shared internally before eventually being returned to Nintendo. Or at least, they should have been returned.
Never officially released to the public, the systems were shipped to stores alongside a game cartridge called eCrew Development Program, which teaches new staff how to cook and serve items from the McDonald's menu using a food preparation simulator and includes player profiles and performance statistics for managers to assess.
A very small handful of these units have sneaked out into the public (five are known about if you believe Wikipedia), and one of them is owned by Twitter user, @XX_750000. Over the past few months, they've been sharing photos of the system, as well as detailed looks at the manuals which come with the included cartridges.
Here's the manual for eSmart 2.0, a newer and rarer version of the training program:
If you're wanting to get your hands on one of these yourself, well... Good luck. They're so rare that spotting one for up sale is a hard enough task itself, and when they do appear, they don't come cheap!