My niece and I had these when we were kids, and so did my cousins, who lived across the street from us. Man, we spent hours on the things. Days, even.
Did you have them? Did you call them Hippity Hops, Hoppity Hops, or Hoppity Horses?
We had the red and blue ones with horse heads, and called then Hoppity Horses, I think.
Retroland has some great memories and photos. I love this person's memory: "I never had one, but every time we went to K mart, I'd race to the toy section and grab a Hippity Hop. I'm sure the store employees were not that thrilled with me hopping all over the aisles."
Retroland also lists Hoppity/Hippity Hops/Horses on their list of the Top Five Outdoor Toys, which also includes Frisbee. Super Soakers, Big Wheels and Slip N Slides.
I didn't know anyone who had the ones with the Donald Duck and Mickey Mouse heads, though. But it was soooo much fun to bounce.
They still sell similar toys, but they're not exactly the same.