03/21/2012 09:45 am ET

Jimmy Fallon Bumps Joan Rivers For Whitney Cummings, On 'Joan And Melissa' (VIDEO)

To say that Joan Rivers is a late night talk show veteran would be an understatement. She's practically a late night institution, and on "Joan And Melissa" (Tues., 9 p.m. ET on WE) she was really looking forward to appearing on NBC's "Late Night."

However, as she was being prepped in make-up she got some bad news from host Jimmy Fallon. "I am so sorry," he started, "I am going to have to bump you. ... I feel so bad doing this, we got Whitney Cummings."

Joan tried to keep it together, but couldn't resist having a dig at her younger replacement. "She's funny. Not very funny."

As Fallon kept apologizing Joan started to wonder if it was all a set-up at her expense. "Is this true?" she asked him. "I'm here in New York specifically for this."

Sadly for Joan, it was true, and as Fallon backed out he reassured her that "it's just the business." Eventually, mad that as she saw it she'd been the victim of ageism, Joan stormed out.

"Joan And Melissa: Joan Knows Best?" airs Tuesdays at 9 p.m. ET on WE.

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