ABC worried that viewers would assume that Felix and Oscar were homosexuals because they lived together. As a prank, Randall and Klugman would often improvise scenes with homoerotic dialogue and send them to the network. A few of these can be seen in The Odd Couple Out-Takes (2005).
Early episodes from the first season were titled "Neil Simon's The Odd Couple". Simon objected to this, having nothing to do with the television series, and not wanting to leave the impression left that he did, not knowing the quality of the television scripts. (He did continue to receive a 'Based on the Play created by' credit.) After seeing the first two seasons of the show he became more of a fan of the TV version, and even agreed to appear as himself in a cameo in one episode.
Felix and Oscar live at 74th st and Central Park West. This is mentioned in the episode where Oscar wins a car on the radio from Dick Clark. The pair actually state the address, and in the scene where they win the car is filmed outside the San Remo apartment building, which is actually located on Central Park West, between 74th and 75th streets in Manhattan. Their address is also mentioned several times as being 1049 Park Ave.
Three different stories were given as to how Felix and Oscar met and became friends. The original opening narration to the show claimed that they were childhood friends. Several times during the series, however, it was claimed they met while they were both serving in the army. One episode (a send up of the film 12 Angry Men (1957)) claimed they met while serving on the jury of a controversial murder trial (Jack Klugman, who appeared as a juror in 12 Angry Men (1957), portrayed characteristics of several characters from the film, including his own. Tony Randall portrayed the Henry Fonda character.) In the third season, the word "childhood" was removed from the opening narration.
The original voices of Linus and Lucy from the Peanuts animated programs both appeared in early episodes of the series. Christopher Shea (Linus) appeared in some episodes as the across the hall neighbor Phillip, and Pamelyn Ferdiin (Lucy) originated the role of Felix's daughter Edna.
Tony Randall continually fretted about the show's future as it rarely drew high ratings and was always seemingly on the verge of cancellation. Jack Klugman would often tell Randall not to worry, accurately predicting the show's success and longevity upon its reruns entering into syndication.
During the first season (1970-71), the show was filmed in the same apartment as the one in the 1968 movie in single camera format with a laugh track. Beginning with the second season, the show was filmed in a studio in three camera format before a live audience.
Years after the show went off the air, Tony Randall recalled getting questions about the *true* nature of Felix and Oscar's relationship. Once, Randall and his wife took a cab from the airport to their California home. As Randall's wife walked into the house with a suitcase, the cab driver asked Tony, "Who's that lady?" Randall replied, "That's my wife." The cab driver looked surprised. "Your wife?" "Of course," said Randall. "Who did you think it was?" The cab driver shrugged. "I always thought that...you and Oscar were...you know."
Many of Felix and Oscar's personal interests were drawn from those of Tony Randall and Jack Klugman. For example, Randall was an aficionado of Opera and Classical Music, which was incorporated into Felix. Likewise, Jack Klugman was an avid Horse Racing fan, which Oscar was portrayed to be as well.
Felix and Murray played together in a band that specialized in 1930s music which was called "The Sophisticatos". In one episode, the band played country and western music and went by the name "Red River Unger and his Saddle Sores".
The address of Felix and Oscar's apartment building is 1049 Park Avenue, an actual New York City address. Scenes for the opening credits and exterior views of the building seen on the show were filmed in front of the building. Employees and residents of the building say fans still visit the location looking for Felix and Oscar, and claim that mail addressed to the characters is delivered on occasion.
According to Elinor Donahue, she had trouble with her lines during her first table read with the cast. Tony Randall banged on the table and yelled at her for blowing her lines causing her to cry. The next day, Donahue found a bouquet of flowers and an apology note from Randall. The two ended up becoming great friends.
The name of the paper Oscar wrote for was the New York Herald. It was, in fact, a real newspaper - sort of. It's name was actually the New York Herald-Tribune and it folded in the mid-1960's. It was founded by Horace Greeley.