White Castle is unique even for America.

They were the original "slider", i.e tiny little hamburgers and their founders created what has become the "fast food" concept whereby the cooks are really just technicians who produce standardized product.

Some people refer to their hamburgers as "Gut grenades" because they can feel like they've exploded in your belly if you've had too many.

More likely, the upset stomach can come from the alcohol consumed during the night and people like to go to White Castle for "drunk" food.