On the screen, they had great chemistry. But off screen, some TV and movie couples just didn't like each other. From minor personality clashes to full blown on set feuds, these onscreen lovebirds didn't always see eye to eye off the set. Here are some TV and movie couples that didn't get along in real life.

Fred and Ethel Mertz - I Love Lucy, 1951-1959 (William Frawley and Vivian Vance). This mismatched pair from the classic 1950s sitcom had trouble from the start. Vance never liked the fact that her onscreen husband, played by Frawley, was 22 years older than she was. Furthermore, producers of the show wanted her to look frumpy and matronly to make her marriage to Frawley's Fred Mertz more believable. Early on, Frawley allegedly overheard Vance complaining about having to work with a man that was old enough to be her father. That set the tone for a feud between the two that lasted for the run of the series. According to imdb.com, upon learning of Frawley's death in 1966 while she was dining out, Vivian Vance ordered a round of champagne for everyone at her table.

David Addison and Maddie Hayes - Moonlighting (Bruce Willis and Cybill Shepherd). On-screen these private eyes flirted for two seasons and then sizzled by season three. But off screen, Willis and Shepherd mixed like oil and water. Besides their well-publicized personality conflicts, the birth of Shepherd's twins coincided with Willis' foray into movie stardom, causing an even bigger rift between the two.

Zack Mayo and Paula Pokrifki - An Officer and a Gentleman, 1982 (Richard Gere and Debra Winger). Winger has long been pegged as difficult to work with, so it's no surprise that it wasn't all roses when she filmed this love story with Gere in 1982. There were reports of endless on-set arguing between the co-stars, and Winger has even reportedly said that filming An Officer and a Gentleman movie was one of the worst experiences of her life. You wouldn't know it by watching the movie. Winger and Gere have major chemistry in this film. Guess they're really good actors.

Johnny Castle and 'Baby' Houseman - Dirty Dancing, 1987 (Patrick Swayze and Jennifer Grey). Fans of this dance movie loved how Baby and Johnny moved together, but off the set it was a different matter. In his 2009 memoir titled "The Time Of My Life," Swayze described his co-star as a royal pain, complete with mood swings and diva-like behavior.

Romeo and Juliet - Romeo + Juliet, 1996 (Leonardo DiCaprio and Claire Danes). In this modern version of the William Shakespeare classic, youngsters DiCaprio and Danes wowed critics with their portrayal of the doomed couple. But off screen, DiCaprio was apparently a prankster. The always-mature (for her age) Danes reportedly referred to him as "very immature."

Baby Jane and Blanche Hudson - Whatever Happened to Baby Jane, 1962 (Joan Crawford and Bette Davis). While these actresses didn't play an on-screen couple, they did play sisters in this creepy 1962 movie. The off-screen rivalry between these two actresses is legendary, with Davis even being quoted as once saying "The best time I ever had with Joan Crawford was when I pushed her down the stairs in Whatever Happened to Baby Jane." Over the years, several documentaries have been made about the rivalry between the two actresses.

(source: Yahoo Entertainment)