It may not have attitude, but its fans pay tribute to the design of Dante Giacosa as "a happy car" which is a lot of fun to drive. Quentin Willson admits it has all the performance of a stone snail, a speedomete rthe size of a pocket watch and luggage space fora toothbrush or two. But where other cars are about image and power, the Fiat 500 seems to engender genuine affection among owners past and present. What is the appeal of this matiest of four-wheelers?