If you've never tried to make your cat play with bird/fish videos on your laptop, now is the time. They might not care, or maybe they'll just care for a little while, but for the time that they do care, it'll be the funniest thing you've seen your cat do in a while. No, silly kitty, you can't catch the bird on the screen, but it's sure as heck funny to watch how confused you are.
And goodness, you better hope that they don't accidentally pause the video as they're watching, because the confusion is only going to intensify. Actually, never mind that, pause the video for them and laugh some more. And laugh at this tumblr thread that gives us the best of cats birdwatching on computers while you're at it.