George's father was initially played by 'John Randolph' in the episode "The Handicap Spot". In syndication his guest appearance has been replaced by new footage featuring Jerry Stiller who played George's father in the later episodes. The DVD release of this episode featured in the Season 4 box set allows the option to watch either version.
In the episode "The Summer Of George" some scenes were edited for TV screening but were aired in full in foreign countries during reruns. Extra footage included more dialogue between George and a shop assistant with regard to party invitations, Jerry and his girlfriend discussing who would look after her shopping the coffee shop and a couple more lines between George and Jerry near the end of the episode as George lies in a hospital bed.
In the episode, "Bookstore, The" (ep. #9.17), J. Peterman describes provides several euphemisms for the drug opium when he's describing Elaine's boyfriend's addiction. In the original airing, he referred to it as "smack...white palace...the Chinaman's nightcap". In all syndicated airings, the last part of that line was omitted, obviously because of its racial insensitivity.
'Larry David' was the original voice of Newman in "The Revenge", but 'Wayne Knight' overdubbed the voice for syndication. Both versions are available in the Season 2 DVD set.