In 1995, we did a set of Groo Trading Cards that folks still avidly collect. It's not hard to amass a complete set but it is tough to find these things called "sketch cards." There were fifty of them, I think, inserted randomly into the little packets of cards.
One side of each sketch card was printed. You can see what that looked like above at the far left. Then on the other side of the card, Groo creator Sergio Aragonés drew anything he felt like drawing. The other image above shows you an example.
A couple of avid Groo collectors (there are such people) are attempting to locate the whereabouts of as many sketch cards as possible. Do you perhaps have one? If you do, dropan e-mail and tell him all about it. You'll make the man so happy.