Robin Quivers is known for her sense of humor as co-host of “The Howard Stern Show,” but when she ran and completed the New York City Marathon a few weeks ago, she knew her accomplishment was no laughing matter. “Whew, it was much harder than I thought it would be, but I can’t believe I did it,” she said during a recent phoner with… Quivers, 58, never imagined herself an athlete or running more than three miles a day, much less 26.2 miles in the NYC Marathon. But she did run, and finished in six hours and nine minutes. Always full of laughs, she remembers being so tired around the 15th mile that she stopped at a local bread shop to get something in her stomach. “I thought, ‘I have to get something real, my body can’t do it on this.” The Maryland native was running to raise money for her recently formed charity, the 15 Foundation, whose mission is to highlight people who are doing excellent things for their communities, especially with education. “It was education that helped me have the life that I have to today so I wanted to highlight organizations that are dedicated to improving the educational lives of children,” she says. Running a marathon is just one more thing Quivers can add to her list of things she never “in a million years” imagined she could do; another being losing 80 pounds and becoming a vegan in the last three years. “This has been phenomenal for me and it has changed my life completely.”