Godfather of Harlem, set in 1963, features the South African flag adopted in 1994 on a Harlem boxing gym wall. How many people worked on that show and how much money was spent on it and not one person in the production team picked up on it.
Just started on American Horror Story courtesy of Netflix - absolutely loving it so far (admittedly only 2 episodes in). Great cinematography, great acting, great writing and the pilot episode was something else.