Herr Ampelmann, the Walk/Don't Walk symbol, can be found on just about every corner in Berlin, and in more souvenir versions than you can imagine; he's a symbol not only of Berlin and traffic safety, but also of 'Ostalgie,' or nostalgia for the old days of East Germany.
Herr Ampelmann, or if you want to get technical, the Ampelmännchen, has been called "one of the few features of East Germany to have survived the end of the Iron Curtain with his popularity unscathed." In fact, he's become so popular that he can be found all over Berlin, not just in the east, and in several cities in western Germany.
Celebrating the 25th anniversary of German reunification
An attempt after German unification in 1990 to replace him with a 'standard' or Pan-German version came at just about the time of the first wave of Ostalgie, and resulted in demonstrations and protests that kept him on the job and spread his fame. Some traffic engineers have pointed out that his chubby shape means a brighter signal.
Incidentally, when he was first introduced in 1961 as part of the first pedestrian signals in Germany, he was only part of his designer's proposal. Karl Peglau, the engineer who designed him, pointed out that because there were two different shapes, they were useful even to colorblind people. He proposed a similar shape system for vehicle traffic lights as well, using simple shapes as well as the colors. It was never implemented; authorities said it would cost too much.