By now you've probably seen at least one video of a soldier or Marine returning home and seeing his dog for the first time. It's one of the things the Internet does that really, genuinely tugs at your heartstrings.
Anyone who's ever had a cat knows that cats can find their way into just about anything. So it's particularly amusing to watch them mastering the art of opening the door. It may be simple to us, but remember: we have thumbs.
With all the trouble human beings have working together these days to get anything done—have you watched the news lately?—it's nice to see two different species getting along so well to achieve a simple goal.