 Walter Matthua, who played Oscar in both the original Broadway play  and the movie, actually asked the plays author, Neil Simon, if he  could play Felix instead. This was because Matthau thought Oscars  personality was too similar to his own so the role would be too  easy, whereas playing the persnickety Felix would be a real acting  challenge. Simon replied, "Walter, go and be an actor in somebody  elses play. Please be Oscar in mine." and Matthau finally agreed.