Monica Evans who played Cecily, and Carole Shelley who played Gwendolyn (the Pigeon sisters), are the only actors to play the same roles in the Broadway play, the 1968 movie, and the 1970 TV series.
We learn that Felix and Oscar's doorman is named Harry.
Monica Evans and Carole Shelley who played the Pidgeon Sisters also voice Maid Marion and Lady Cluck in Walt Disney's Robin Hood.