As a child in DeKalb County (Georgia) schools in the early sixties, Safety Patrol kids were rewarded with a train excursion to Washington DC and New York City.
In NY they took us to Chinatown for lunch. Now I had never eaten Chinese in my life so I ordered a hamburger. Saw the mustard sitting on the table so I just did what I normally do....slathered it on.
One bite and the shock and surprise made my eyes get as big as saucers and I wanted to flee and drink up the East River.