There were six wedding cakes made for the wedding scene shoot. One cake was used for a test shot with a stunt woman falling on it to see how it would look. Unbeknownst to director Betty Thomas, there were two wooden spikes inside of the cake for structural support. Fortunately when the stunt woman fell on the cake, she was not wounded.
Toward the end, when Gwen (Sandra Bullock) is back home, she is seen carrying groceries in a Jefferson Market shopping bag. That market was located on 6th Avenue between 10th and 11th Streets, in NYC, had been in existence since 1929, and was considered a true NYC landmark. It closed permanently in 2011, eleven years after 28 Days was released.