George Clooney and several other stars are reacting to the passing of Walter Cronkite. ET cameras rolled at the TV news legend's 90th birthday less than two years ago, when he encouraged Clooney to run for office during his speech.

"He was the most important voice in our lives for thirty years," Clooney says in a statement. "And that voice made people reach for the stars. I hate the world without Walter Cronkite. "

"The Brady Bunch" TV mom and actress Florence Henderson was also touched by the veteran TV journalist, telling ET, "I knew him well. We shared a love of boats. I performed at the first Kennedy Center Honors when he hosted. I think every reporter owes him a debt and every journalist today and in the future should be required to study everything he did."

Veteran actress Carol Channing tells us of her close friend, "I adored both Walter and his wife Betsy. We were together often. He had worked as a theatre reporter covering vaudeville and he knew everyone. I just loved to hear his stories. Oh he was so funny. He and Betsy were a wonderful couple. Betsy loved to tease him, well both of us really, but he loved it."

John S. Hendricks, founder and chairman of Discovery Communications, tells us of his friend and mentor: "It is fair to say there would be no Discovery Channel without Walter Cronkite. ... His guidance, support and commitment were instrumental in securing the resources and distribution to first launch Discovery in 1985. He remained a friend, mentor and invaluable counselor to me. ... I will miss him greatly, and on behalf of the 4000 Discovery employees worldwide, we mourn the passing of our dear friend and colleague who inspired the world with his boundless sense of curiosity. We will continue live up to his standard of excellence and integrity in everything we do each and every day."