When we were very young

I was recently reminded of an incident. It was my birthday - I'd guess maybe 7th. I was given a toy. It was a plastic box, and a roll of paper with a long continuous outline picture on it was inside it. Two knobs held the paper such that by turning the knobs, you could wind the paper back and forth so a different portion of the picture was visible through the clear plastic "screen". It came with wax crayons. The idea was to colour in the picture by crayoning on the screen, then wiping it off, moving the paper back and forth to get another bit of the picture, and then colouring in that part instead. Hours of fun, and you could recolour the same part over and over again, if you wished.

Well, there I was, colouring, wiping, moving the paper, colouring, wiping and moving the paper... and I got to the end of the paper. I looked at what it said, and burst into tears. I ran to my mum with it in hand.

"What's wrong?" she asked.
"It's broken!!" I cried.
"What happened?"
"I don't know... but it's ruined... see? It says so right there!"

And there, at the end of the paper roll, in big letters, it said:

R E W I N D