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.
At the conclusion of the show's run, Felix remarried Gloria and moved out of the apartment.
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.
In one episode, characters from the show walk down the street in New York City and encounter playwright 'Neil Simon'. Simon wrote the play on which the show was based.
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".
A frequent guest star was Monty Hall, who appeared as himself. Apparently, he and Oscar had been college roommates.
The two episodes of the series that featured ABC sportscaster Howard Cosell increased the ratings of the show.
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.
After the show was canceled, Tony Randall won an Emmy for playing Felix Unger. As he accepted his award, he said he wished he "had a job".
Besides Nancy Cunningham, Oscar had another girlfriend that he frequently mentioned named "Crazy Rhoda" Zimmerman. However, unlike Nancy, Rhoda was mentioned but never seen.
Felix's father was an optometrist in Chicago. In fact, one of his father's patients was Oscar's father.
Felix's children were named Leonard and Edna. Tony Randall's real first name is Leonard, and his sister's name was Edna.
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) claimed they met while serving on the jury of a controversial murder trial (Jack Klugman, who appeared as a juror in 12 Angry Men, 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 part of Oscar's (Jack Klugman) ex-wife Blanche was played by Brett Somers, Klugman's own wife. The real life couple were separated during the run of the show.
In the show, Howard Cosell and Oscar Madison were supposed to be arch enemies.
Jane Dulo played Oscar's mother, then played Murray Greshler's wife, all in Season 3.
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."
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) (V).
Art Carney and Dean Martin were considered for the part of Felix. Carney originated the role of Felix in the Broadway play.
The show's Nielsen ratings were low and the show was always near cancellation. But high ratings for the reruns during the summer months would help get the series renewed.
Felix and Oscar's apartment was located at 1049 Park Avenue, an actual New York City address. Exterior views of the building seen on the show, including scenes in the opening credits, were of the actual building at that address.
The iconic narration during the opening credits says that Felix was forced to move out of his residence on November 13. November 13 is the birthday of the show's Executive Producer Garry Marshall.