Invented 1949 in Berlin by a woman who served the people from a small shack, it was called the steak of the poor. Sausages are eaten all over Germany for centuries and the combination of past war ketchup (or homecooked tomato sauce) and a mild curry powder started the boom of this kind of dish. Today even vegan curry sausages are well liked.
You can find lots of food trucks serving this dish. The curry sauces have different types of chili content, you will get it from 1 to 10 on the Scoville scale.
This streetfood spread from Berlin all over Germany. The kind of sausage used, varies a lot. Pure pork, mixed pork and beef and pure beef. Even chicken sausages are offered. Some are grilled without the casing.
The top German car manufacturer VW with his many production places has its own sausage production and they have their own brand of VW ketchup. All the workers can eat them daily if they like and a some are sold outside.
I have a friend who worked there and he sometimes bought a package of VW curry sausages and a bottle of VW ketchup for me. The funny thing is, the sausages are packaged in the same plastic foil, as all other original car parts are shipped to customers too. The writing on the plastic wrap says: VW ORIGINALTEILE