Ryan Reynolds and More Stars Mourn Betty White After Her Death: 'What an Exceptional Life'

The world is mourning the death of Betty White.

White died on Friday at age 99, PEOPLE has confirmed, just two weeks before she would have celebrated her 100th birthday.

"Even though Betty was about to be 100, I thought she would live forever," her agent and close friend Jeff Witjas tells PEOPLE in a statement. "I will miss her terribly and so will the animal world that she loved so much. I don't think Betty ever feared passing because she always wanted to be with her most beloved husband Allen Ludden. She believed she would be with him again."

Following the news of her death, Hollywood's biggest stars shared tributes to the beloved actress.

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"The world looks different now," wrote Ryan Reynolds, who had fostered a loving relationship with White over the years. "She was great at defying expectation. She managed to grow very old and somehow, not old enough. We'll miss you, Betty."

Fellow comedian Ellen DeGeneres called White's life "exceptional."

"I'm grateful for every second I got to spend with Betty White," DeGeneres wrote on Twitter. "Sending love to her family, friends and all of us."

As the world prepared to ring in a new year on Friday night, Andy Cohen wrote: "Tonight we will raise MANY glasses to the WONDERFUL legacy of Betty White!!!"

"Our national treasure, Betty White, has passed just before her 100th birthday," wrote actor George Takei. "Our Sue Ann Nivens, our beloved Rose Nylund, has joined the heavens to delight the stars with her inimitable style, humor, and charm. A great loss to us all. We shall miss her dearly."

LeVar Burton wrote: "Y'all, with the passing of #BettyWhite we have lost one of the best humans ever!"

Kathy Griffin shared stories about several of her favorite encounters with White in a lengthy Twitter thread on Friday.

"Betty White. Where do I begin?" Griffin wrote. "I've known her long, but I think the first time I met her was when she was a guest star on Suddenly Susan in the late 90s. Everyone was very excited she was on the show. I had accidentally parked in her parking spot that day. She walks in... yells from the back of the soundstage for everyone to hear 'Where's that redheaded bitch who stole my parking spot???' SWOON. A friendship was born."

Journalist Dan Rather called White "a spirit of goodness and hope."

"Betty White was much beloved because of who she was, and how she embraced a life well lived," he wrote on Twitter. "Her smile. Her sense of humor. Her basic decency. Our world would be better if more followed her example. It is diminished with her passing."

American Idol alum Katharine McPhee shared a photo of White on her Instagram Story, writing: "Omg 😭😭😭 Americas favorite everything!! RIP Sweet Betty"

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White's Hot in Cleveland costar Valerie Bertinelli also shared her condolences on social media.

"Rest in peace, sweet Betty," Bertinelli wrote. "My God, how bright heaven must be right now."

President Joe Biden and First Lady Dr. Jill Biden also addressed White's death on Friday, according to CNN.

President Biden called her death "a shame," adding: "She was a lovely lady."

"Who didn't love Betty White? We're so sad about her death," Dr. Biden said.

Dionne Warwick wrote on Twitter: "Another brilliant talent has made her transition. I had the pleasure of getting to know Betty White and shared a few giggles with her. May she rest in well-earned peace."

Retweeting PEOPLE's cover story for White's 100th birthday, published just days before her death, Holly Robinson Peete wrote: "NO WAY!!! Rest In Peace Betty White"

Halle Berry also shared a tribute to White, alongside a photo of the actress holding one of her five Emmy awards.

"Thank you for being a friend, Betty! Your INCREDIBLE legacy lives on forever," Berry wrote. "You set the standard for so many to follow. May you rest in eternal peace our forever golden girl."

Actress Diane Kruger also mourned on social media, writing alongside a an old photo of White that she thought the comedian "was supposed to live forever."

"Thank you for the joy you brought ❤️" Kruger wrote on Instagram. "I love you forever ❤️"