Currywurst is an iconic German fast food dish. A sausage is steamed and then fried, sliced, and then topped with curry powder and ketchup. Allegedly it was invented by Herta Heuwer in Berlin in 1949. There are many regional varieties. In Berlin, a sausage without sausage casing is used. A bread role or fries are served as sides. Famous Currywurst joints in Berlin are Konopke's in Prenzlauer Berg and Curry36 in Kreuzberg. My favorite one though is Fritz & Co and Witty's (by the same owner) just in front of KaDeWe. For more details see Wiki.