Topps Sonic the Hedgehog trading cards. This was the first series of cards released in the 1990s. (There was not another American series until the Sonic X cards) These were sometimes base-ball card like, and some had stickers which you could peel off. Mostly, they just took screen shots from the Sonic games (Sonic 1, Sonic 2 = all they had access to at the time) and added in various stock art. This caused a rather lame effect, as you can see the stock art was not much good. What is that horrible monster behind Sonic on the card pack?

They usually had tips or descriptions on the back, and sometimes an extra little scrap of stock art. The rarest of these are the Prism Cards. You are unlikely to find any of these. It is thought that there are 4 different prisms. These are somewhat like silver-ish holograms but not-so-3D.