You see this?
This is an NTAG215 chip. This is the chip that sits in the base of amiibo figures. When you touch this chip to your Nintendo Switch or other console, it scans the amiibo into the game.
Amiibo cards take that chip, program it to be a specific amiibo, and then cover it with a nice image. Nintendo programs their own official Animal Crossing amiibo cards, but you can also find fanmade amiibo cards of every known amiibo on Etsy as well. Just search “amiibo card” and you’ll find plenty of dealers.
There’s also other applications of this as well. For a brief period, I had my own Etsy shop and sold 3D-printed figures with amiibo chips on them. The sky really is the limit when it comes to what you can do with amiibo: if you can slap an NTAG215 chip on it, you can make it an amiibo. I 3D-printed these medallions, and they sold very well.
I don’t recommend trying to start an online store and selling amiibo cards yourself – it’s a highly competitive and small industry, and demand for them is very inconsistent. But if you do try it, I’ve written a guide for new sellers on Etsy to get started.