I still recall, I think it was two years ago, when the Alpha Hound took me by a White Castle in NYC. When we got home, I learned that the burgers all had ketchup on them, something that would never occur in Chicago, where sliders are adorned with only pickle and onion.
I'm usually a ketchup/mustard person, but I have no room for them on a White Castle. But I admit to consuming the ketchup-topped burgers this one time, as I figured a White Castle with ketchup was better than no White Castle at all. We can't get them here in DC, except in the frozen case at the store, and I'm not going there.
So, how do they dress White Castles in other cities?