If you grew up in the '70s, do you remember a toy called the Magic Slate?
It was a little gray sheet of plastic that came with a little red pencil-type thing. You'd draw on the plastic, and then lift it up to erase it. The pencil would dig into the tar-like stuff underneath.
These were inexpensive toys, but they'd wear out after a while. In my day, we had a Bert and Ernie slate, and we may have had a Bugs Bunny slate too.
One of the most hilarious things took place when I was about 4 years old. I had a Magic Slate, and my dad used it to draw a sketch of the Number Painter on 'Sesame Street'. I thought that was so funny!
I had one of those in the mid 90s. I think I got it in a Wendy's kid's meal. Mine had red plastic and drawing on it would cause brighter red to show through, almost a neon pink.
They're not too dissimilar to how carbonless copy paper works.