The Nintendo 3DS comes with six “AR cards” that allow it to play augmented reality games (here’s a quick example if you don’t know what they are) such as a Billiards game or a dragon shooting game.
Some of these are for proper AR games, while others just display Nintendo characters in your surroundings or let your Mii walk around on your dining table when viewed through the 3DS.
With smaller accessories like the AR cards, there’s always a chance that you could lose them. Luckily, Inside Games report that in the event that you do lose your AR cards, you can simply print out new ones. This can be done via this PDF file.
Alternatively, you can also buy new AR cards in Japan for 500 yen.
Note: We aren’t sure if the cards in that PDF will work with a non-Japanese 3DS yet.