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The Insider's Brooke Anderson chatted with the "busiest woman in show business," Joan Rivers, as the comedienne shot her guest starring spot on Hot in Cleveland, playing Betty White's twin sister.

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Liza Minnelli to Guest Star on Hot in Cleveland

"Betty White and I have always been sexual rivals," quipped Joan, jokingly explaining how she was cast in the part. "We've shared a lot of sex partners so it was just inevitable."

As Betty just turned 90 and Joan is only 78, a lesser actress may have been insulted at the idea of playing the twin sister of someone 12 years her senior. It should come as no surprise that Joan had a sense of humor about the situation.

Watch: Behind The Scenes of Hot In Cleveland

"Mother had a very difficult birth -- a long, difficult birth," Joan kidded.

Hot in Cleveland airs Wednesdays at 10 p.m./9C on TV Land.