I "stole" a police cruiser once. All of ours were/are mostly keyed the same. It was at a festival and I had parked the one I had down on the main street just outside the main festival area that was barracaded off. I was on foot for quite a while, it was very hot and I was getting tired and very thristy. I walked back to get in "my" car and came upon another one first. It was parked one street over from where I had parked mine, but at the time I didn't realize it was not mine. I got in it drove about 2 miles to a store with the AC full blast, bought a gatorade, drove it back to park it in the same place I had parked before only to find that my car was still right there, OOPS. I then realized what had happened and drove it back to where it had been parked. I thought I was home free but just as I stepped out the other deputy was rounding the corner and saw. He would have never known what really happend I could have just said I was using the radio or something, but I told him the whole story and we laughed about it, especially about how he would have been thinking it was stolen if I hadn't been just a minute later getting back. The funniest part is that although the two crown vics looked identicle on the outside they differed quite a bit on the inside in how some of the equipment was mounted and it had cloth seats vs. the vinyl in the one I had.
It was then that I decided I needed a vacation.