A Gatsby is Cape Town's answer to a Hoagie -- large enough to share, and filled with slap chips (flaccid, thick-cut, vinegary potato chips), meat, sausage or fish, and often livened up with spicy pickled green mango atchar. The story goes that Rashaad Pandy, a shop owner in Athlone, used what he had to hand to rustle up improvised Hoagies for some day-labourers. A man called Froggy exclaimed "Gatsby smash!". Nobody knows what he meant other than that he liked it. A lot. A Gatsby is supposedly an excellent hangover remedy among people who know about such things.
Durban's iconic Bunny Chow is a hollowed-out half loaf of white bread containing a generous portion of curry and traditionally served with grated carrot and no cutlery. It has nothing at all to do with rabbits. The "bunny" part of the name is a corruption of bania (Indian merchant); so a bunny chow is literally food from the Indian corner shop.