Why and how these caught on, I have NO idea but I had some. These little round cardboard disks are called POGS. Where I grew up they sold them at the local movie rental place, Mavericks. My sisters and I had TONS of them we traded them and won them from each other and friends. If I remember correctly you make a small stack and take turns hitting the stack with a "slammer." Whichever ones flipped over you won and got to keep. The slammers were the same circle shape, just a little thicker and heavier, and made out of some metal or plastic. The POGS were kept in a long cylindrical case with a screw on top. I remember having a lime green one. they were all the rage... but quickly fizzled out.
Did You have any POGS? Did your kids?