If truth, as they say, is stranger than fiction, sometimes it's also more compelling. In their new film, "The Sessions," costars John Hawkes and Helen Hunt found plenty of inspiration in their characters' real-life counterparts: the late Mark O'Brien, an author confined to an iron lung after contracting polio as a boy, and Cheryl Cohen Greene, the sex surrogate he enlisted to help him lose his virginity at age 38.