I was at the grocery store tonight on the way home from work and saw
this toy in the pet food aisle.  It is a mouse on wheels inside of a
ball, sort of like a hamster ball where you let them roll around the
house.  I had to buy it.  LOL  Never get sucked into cat toys over
$5. My gang were intriqued and chased the ball around while the mouse
rolled on, but I think they were more afraid of it than entertained.
The thing moves like a living creature with its quick turns and the
ball gets stuck up against furniture, then the mouse turns over and
its as if it died. It was fun watching the kitties get all curious
about it though.

It's pictured at the botom of this page:

http://www.ourpets.com/products_it2.html