This is known as a truck limo. They come in various styles and lengths. I saw one like this with the pick-up bed on the back end the other day. Wish I had taken the camera with me but you will just have to imagine.
Because it was this hot pink color!
These things are very popular for parties and weddings. Especially for prom nights. A good idea to keep the party goers from having accidents, but only available to those who have cash to throw around. One site I looked at charged $100 an hour, 5 hour minimum. And that would not include the gratuity for the driver which I suppose would be another 15-20%. Regular limos are strange looking enough, stretch limos more so, but the truck limos with the pick-up beds are downright bizarre. I did find one photo with what you do with the pick-up bed....they had a bikini clad girl in it and it was filled with water and rose petals.