He pitched to Willie Mays, suited up for the Celtics, stepped into the ring with Archie Moore and even took a few snaps as quarterback for the Detroit Lions. But George Plimpton was no athlete.

He recalled a story that Plimpton once told him about Ernest Hemingway. While visiting the adventurous novelist at his home in Havana, Cuba—where Hemingway wrote “The Old Man and the Sea ...