U.S. Patent No. 5,443,036 (.pdf)
Here's a classic example of what my dad would call a PGO: a Penetrating Glimpse of the Obvious. If you've never thought of using a laser pointer as a cat toy then, well, you've probably never seen a laser pointer or a cat before. As the inventors so eruditely point out, cats like to chase moving lights, and laser pointers can be used as (oh my god!) moving lights. Put the two together aaaannnndddd... yeah, your cat runs around and gets some exercise. Try reading it twice if you need some time to wrap your head around the concepts at heart here - they're pretty deep.
And don't forget, the next time you try to make money off of teaching your friends to use a laser pointer to mess with their cats, a lawsuit sits right around the corner.