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. From Wikipedia: The Wiffle Ball is about the same size as a regulation baseball, but is hollow, lightweight, of resilient plastic, and no more than 1/8 inch (3 mm) thick. One half is perforated with eight .75-inch (19 mm) oblong holes; the other half is non-perforated.