41 Inches Tall and Completely Street Legal
Perry Watkins' clownish mini car, "The Wind Up", is officially the world's smallest street legal vehicle, standing at 41 inches high, 51 inches long and 26 inches wide. The wind up mechanism is purely cosmetic; the car operates as a regular-sized car does, with a tiny engine that can go up to 60kph (37mph).
Note: This isn't Watkins' first bizarro vehicle. He unveiled his 100mph, 19 inch high "Flatmobile" a couple years back: