If you watch BTTF II very carefully, the scene where Marty goes to the future and arrives in town you see futuristic cars going back and forth on the street from the alley. Two of them are Pulses, a 4 wheeled motorcycle. I always thought they were prop cars for the movie. They are actually hand-built autocycles, about 350 were built back in the 80's in Michigan. Designed by Jim Bede and built by the Owassa Motor Car Company. For more information visit autocycles.com I just bought #288. It needs a lot of "love" to get everything to work and look pretty again. You can see pictures of a Pulse parked on a back lot next to a Delorean.