Stars React to the Death of Joan Rivers

Legendary comedian Joan Rivers passed away Thursday, September 4, at the age of 81, leaving Hollywood in mourning.

"It is with great sadness that I announce the death of my mother, Joan Rivers. She passed peacefully at 1:17pm surrounded by family and close friends," her daughter Melissa Rivers confirmed in a statement. "My mother's greatest joy in life was to make people laugh. Although that is difficult to do right now, I know her final wish would be that we return to laughing soon."

Here's a sampling of the massive celebrity response to the passing of the comedy legend.

"[She was] obviously a hugely influential gal," Robert Downey Jr. said at the premiere of The Judge at the Toronto Film Festival. "Our thoughts are with her family."

"I was just simply fond of her," Sarah Jessica Parker told ET at Gareth Pugh featured at Lexus Design Disrupted, which kicked off New York Fashion Week on Thursday. "And though she had experienced more years than some of us, I still felt that there was so much life."

More stars spoke to ET at the Ping Pong 4 Purpose event benefiting Kershaw's Challenge, a Christian organization that focuses on helping people in need.

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Andy Cohen: "I love this ballsy, funny, generous, shrewd, unpredictable and loyal woman. I grew up in awe of her as she filled in for Carson and pinched myself when I co-starred in a pilot with her for Bravo in '06. She went on to appear on WWHL many times, showing up in the middle of the night with a great attitude and a slew of new jokes. And this summer Michael Rourke and I developed a show with her, starring her, that we were in the middle of pitching networks. She was so indomitable we all thought she would live forever. Joan was a trailblazer and an indelible part of pop culture."

Rosie O'Donnell: "At opening night of A CHORUS LINE - 2006 - she as usual made fun of my "lesbian challenged black tie" - xxxx - thank u Joanie!!"

Ariana Grande: "rip Joan Rivers :'( the MOST fabulous and hilarious. Frankie and I saw her live and met her multiple times together, we loved her so so much. Heartbreaking. Rest in peace Joan, u will be so missed!!"