Joan Rivers is no stranger to insulting celebrities with her brash brand of humor, but this time it could land her in some legal hot water.

The 81-year-old outspoken comedienne recently revealed that she is being threatened to be sued by Kristen Stewart over a reference to the actress' affair with married director Rupert Sanders, which Rivers makes mention of in her upcoming book, 'Diary of a Mad Diva.'

"I'm now being sued by Kristen Stewart," Rivers tells a paparazzo in a new video (which you can watch on TMZ). "She obviously did not read our disclaimer, which is that it is a comedy book. And I can't wait to get her to corporate, 'cause I want to get a puppet, and I want her to show me on the puppet where she thinks I claim she touched her director."

According to TMZ, the passage in question reads as follows: "Many stars only do one thing well. Of course, the best one-trick pony is Kristen Stewart, who got a whole career by being able to juggle a director's balls." Stewart's lawyer is reportedly suing for defamation -- though the site also reports that she may have possibly backed down.

"Her lawyer contacted my lawyer," Rivers continued in the video. "Which shows the sense of humor she has. Zero. My answer her to her was: Be glad you're not a Kardashian. Because they're featured a lot more in the book."

When the paparazzo revealed that he had never seen Stewart smile, Rivers was quick with another joke.

"Well, she has no teeth. Which made her much better in bed when she was doing what I said she was doing," Rivers remarked crudely. "Allegedly," she added.

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