 In the episode "Viva Ned Flanders", Homer and Ned are at the roulette table.  While trying to pick numbers, the original airing has Homer saying, "When are  the kids birthdays? Barneys is April 20th, same as Hitlers." After the  incidents of Columbine High School a few months later, the episode ran again  in a repeat and changed Homers line from "April 20th" to "June 15th, same as  Lassies." When "Viva" hit syndication, it looked as though they kept it  April 20th.