Wiffle ball was invented in 1953 by David Mullaney who wanted a ball, that was really easy to curve, for his 12 year old son. It got its name because they would refer to a strikeout as a whiff.
I loved playing in my backyard with a friend. You can throw all sorts of exaggerated curves. I used to hit with my regular baseball bat, which was good practice for the real thing. The ball, on the left, is one I actually used as a kid (notice the repairs!)
The Variety Store, in Alpharetta Georgia, always carried Wiffle balls that came in boxes like the one above.