In the fifth year of Hill Street blues, a regular extra, Robert Hirschfield who played desk clerk Leo, started to get an opening credit... That is instead of getting an end of show "also starring" mention... I noticed, on maybe episode 15 or 16 that he was getting credit at the end of the show as well as at the beginning. An oversight, obviously. He had been relegated to the end of the show credits for so long, likely over 90 episodes, I found it funny.