Joan Rivers and Rihanna are the latest celebrities to have a spat via Twitter. On Friday, Rivers tweeted a joke about Rihanna's past domestic abuse at the hands of Chris Brown after the pop star confessed she still loves the rhythm-and-blues singer.

"Rihanna confessed to Oprah Winfrey that she still loves Chris Brown. Idiot! Now it's MY turn to slap her," Rivers tweeted.

According to Radar Online, the "Umbrella" singer responded to Rivers' comment by tweeting, "[W]ow u really do get slow when you're old huh?"

During an interview with Oprah Winfrey on "Oprah's Next Chapter" last week, Rihanna tearfully detailed how the 2009 abuse Brown put her through changed her life and affected the public's image of her. Despite criticism from the tabloids and her own fans for maintaining a relationship with Brown, Rihanna admitted the erstwhile lovers are "still close" and they will "always love each other."

Entertainment Weekly reported that perhaps the most shocking statement by Rihanna was "we have maintained a very close friendship since the restraining order was dropped." Oprah was supportive throughout the conversation, at one point telling Rihanna that she is not a victim because of her decision to forgive Brown.

Rihanna, who at only 24 years old is one of the most popular singers in the world, made sure to add that it was her own personal decision to put the abuse behind her. At 79, Joan Rivers is more than 50 years older than Rihanna. The comedian is known for her sometimes brutal critiques of stars in the public eye.

Fans of hers will remember that Rivers was in the news this month for handcuffing herself to a shopping cart during a protest at a Costco store. According to E! Online, Rivers went through the store with a megaphone attached to the cart because the chain had announced it would ban her newest book, "I Hate Everyone ... Starting with Me." It's possible that the Costco incident and the Rihanna joke were publicity stunts to gain attention for her new book, which has appeared on the New York Times best-seller list.

Rivers first came into the national spotlight by appearing on late-night television talk shows, even guest-hosting for the legendary Johnny Carson on "The Tonight Show Starring Johnny Carson." She's regarded by many standup comics today as one of the best ever. Among her comparatively recent TV gigs, she appeared in an episode of "Louie," the critically beloved FX show created by comedian Louis C.K.

In recent years, Rivers has appeared on the E! and TV Guide networks making fun of what celebrities wore on the red carpet at major awards shows. She's also famous for the amount of plastic surgery she's had done, something that's been both criticized and praised by her own fans.

The comedian frequently performs in Las Vegas, although she is known for her tireless work ethic around the world. Reuters reported Friday she's preparing for a European tour shortly after helping raise money for a community center operated by a voodoo priestess in New Orelans.