Since we're on the topic...
We were taking care of a dog for some friends a couple weeks ago while they wee out of town. Our schedules didn't mesh completely -- we needed to be at my sister's place for a few days at Christmas and she didn't want an extra dog coming -- so we arranged to drop the dog off at a boarding place for a few days in the middle. The dog, Nico, didn't know us very well so he was pretty aloof most of the time, but he started to relax by the time we needed to drop him off at the boarding place.
The day we needed to board him, my wife first took him on a long hike with our dog, then delivered him to the boarder. The next morning, our dog Sunny starting barking like there was someone at the door. When my wife checked to see who was there, Nico was waiting there with his tail wagging and let himself in.
The amazing thing is that the boarding place is about 5 miles away form our house, and there were quite a few busy streets to cross in between. My wife was quite touched that he wanted to get back to us so badly. Dogs -- what are