It's not what you think. It's dumber than that.
Currywurst is a traditional and popular fast food offering found in Germany. It is a bratwurst, often cut up, and covered with curry ketchup. Curry ketchup is ketchup with curry powder. It is usually served with french fries and/or bread rolls.
Currywurst was invented (or possibly popularized by) by Herta Heuwer, a food kiosk owner in Berlin; her only claim to fame is the invention (or, possibly, popularization) of the currywurst, but that's enough to make her famous. By legend, on September 4, 1949 she served a sausage first boiled, then fried, in a sauce of tomato paste, Worcestershire sauce, curry powder, and other ingredients. This sauce was trademarked under the name Chillup, but inexplicably is not sold in stores. To be clear, you can buy pre-made, derivative currywurst in grocery stores, but it will not have the original Chillup sauce.
Currywurst is still generally available in Germany; it is especially popular in Berlin, where it was invented. It is a minor political tradition for anyone standing as a candidate for the mayor of Berlin to be photographed at a currywurst stand, and in 2019 the Berlin State Mint issued a commemorative currywurst coin. From 2009 to 2019 there was a Deutsches Currywurst Museum in Berlin: highlights included a 3D snack bar map of Berlin (sadly, there is no explanation as to why 3D), a fast food stand with different types of sausages and sauces (including vegetarian options!), a curry mix smelling station, "Herta Heuwer's kitchen", and Clips about currywurst from popular German TV shows. They also had a currywurst-mobile (like the Wienermobile, but spicier!)
Also, of course there is a song about currywurst, named Currywurst, by Herbert Grönemeyer, released in 1982 (YouTube link).