We have a Cairn Terrier who likes to chase all sorts of things that dart around. By his breed he should be fascinated and want to catch mice, gopher and rats.
We recently bought our cat a laser to play with. It has turned out that that our dog loves it as much as the cat. I imagine some day that the dog and cat will smash heads one day when they both attempt to capture the light. It almost makes me laugh to imagine them like two stooges hitting heads and falling back stunned. Hopefully I will have a camera handy when it happens.