Noodles or macaroni, and a bunch of other stuff all in the same dish. But apparently, according to school lunch people, kids today don't even recognize casseroles as being food. This, they said, is because they never see casseroles at home. Nobody makes them anymore. Another generation and the casserole will be a lost art.
Casseroles are the food of the poor to middle class.
Take a little bit of something, and make it stretch by adding pasta and a can of cream of mushroom soup. Cheap and filling. If you want it fancy, crush up some potato chips on top. Maybe the same thing will happen to casseroles that happened to other sorts of poor folks' food. There was a time when spare ribs were practically throw-away meat.