Identical Cousins: The Patty Duke Show

For some inexplicable reason, the show's theme song declared that a hot dog makes the all-American Patty lose control, while Cathy is more of a crepe suzette kind of girl.

A little-known band called the Skip-Jacks sang the theme songs for both Patty Duke and the Flintstones. That may explain why the "Identical Cousins" tune sounds just a little bit like the "Meet the Flintstones" ditty.

The show was filmed on location in and around New York and is officially set in Brooklyn Heights. Producers chose New York over Los Angeles because relaxed child labor laws allowed Duke to film for longer hours.

Cathy grew up in Scotland, but thanks to her globe-trotting father, she has been everywhere from Zanzibar to Barclay Square. She moves in with Patty's family so she can attend high school and stay in one place while her father travels for work.

The girls were identical cousins because their fathers were actually identical twins. William Schallert played both Martin Lane, Patty's dad, and Kenneth Lane, Cathy's father, on the show.

Patty's dad was the managing editor of the "New York Daily Chronicle," while Cathy's dad was a foreign correspondent for the same publication.

Patty and Richard Harrison, played by Eddie Applegate, dated throughout the series -- though Patty often broke up with him when another guy caught her eye.

Actor Paul O'Keefe played Patty's younger brother Ross Lane on the show. While the pair often got along, Ross wasn't above blackmailing his sister or playing pranks on her occasionally.

Patty goes from flunking French to acing the class after she falls for her substitute teacher Andre Malon in the series premiere. Malon takes a special interest in Patty because she is struggling with her grades, not realizing that he is actually leading her on.

Patty wants to surprise her father with a trip to the fishing lodge where he spent his honeymoon. When she goes to pick up a fishing license for the trip, her father's boss sees her and Richard and assumes they are getting ready to elope.

Cathy really wants to play Cleopatra in the school production of "Antony and Cleopatra" during Season 1, but Patty gets the role instead. When Cathy is named understudy, she is ready to take over the part when Patty falls ill.

The entire Lane family is thrilled when Martin's newspaper wants to send him -- and his wife and kids -- to Paris for a year. Once they realize how much they'll be leaving behind, though, they opt out of moving to France.

What woman doesn't want a vacuum cleaner for her birthday? When Cathy decides to purchase the vacuum from a traveling salesman, she gets more than she bargained for and asks Patty for help in paying for the machine.

Patty takes up the tuba in the Season 2 premiere but drives her family to wear ear plugs with her persistent practice.

Patty Lane and Sue Ellen Turner -- played by Kitty Sullivan -- are often at odds in the first two seasons. The two girls, who go to school together, typically fight over boys -- and Sue Ellen even has the nerve to try and woo Richard at one point.

Patty lies about her age to join the Peace Corps in Season 2. She's accepted for a mission to Africa and starts learning Swahili before her family finds out and stops her from going.

After seeing her father investing in the stock market, Patty decides to start her own corporation and seek out investors. She starts Patty Lane, Inc. to sell Cathy's homemade apricot jam.

Frank Sinatra Jr. guest stars in the Season 2 episode "Every Girl Should Be Married." In the episode, he plays David Stone, a boy that Patty believes her parents are trying to force her to marry.

In addition to playing Patty and Cathy, Patty Duke also played another identical cousin, Betsy from Tennessee -- who is the daughter of her father Martin's brother Jed and happens to look just like Patty and Cathy.

Singer and actor Frankie Avalon is driving past the Lane's home when he has the bad luck to break down in the Season 3 premiere "A Foggy Day in Brooklyn Heights." When he knocks on the door for help, Patty is determined to spend as much time as possible with the teen idol.

Fifties teen idol Troy Donahue plays Dr. Morgan, who gets Patty's heart soaring when he removes her tonsils in Season 3.

Ross desperately wants to join the Tigers Basketball Club in the series finale of the show. The club will only let him in if Patty agrees to go on a date with the club president, but Patty can't stand him.

Poor Patty can't catch a break; after dealing with Sue Ellen Turner for years, Patty starts feuding with Monica Robinson -- played by Kathy Garver -- throughout Season 3.

Patty may be the boy-crazy one, but Cathy has a boyfriend of her own throughout Season 1. Played by Skip Hinnant, Ted appears in around half a dozen episodes in Season 1 before he disappears.

"Still Rockin' in Brooklyn Heights" came out in 1999 -- more than 30 years after the show went off the air in 1966. Actress Patty Duke reprised her dual role as Cathy and Patty.

Sue Ellen is at it again. This time, she wants to tear down the high school -- where Patty happens to work -- so she can build a shopping mall.

Kitty Sullivan wasn't available to play Sue Ellen on the Patty Duke reunion. Instead, Cindy Williams -- who played Shirley Feeney on "Laverne and Shirley" -- took over the role of Patty's rival Sue Ellen.

In the reunion special, Patty and Richard have split up, but they have a son named Michael and a granddaughter named Molly. Cathy is living in Scotland with her son Liam.

When producer Sidney Sheldon was creating a show for actress Patty Duke, he had her spend a week with his family so he could get to know her. This gave him the idea for "The Patty Duke Show," which was based on the two distinct sides of the actress' personality. She was later diagnosed as bi-polar, which may explain her very different personas.

"The Patty Duke Show" ran for just three seasons between 1963 and 1966. The show ended over disagreements between switching from black and white to color and over fights about moving filming of the show from New York to California.