If you ever look closely at Jackie Gleason’s final onscreen moments, you understand why “The Great One” earned that title in a way few comedians ever done. Behind the scenes, Gleason was living with serious health problems, including colon cancer and diabetes. But he refused to allow cameras to show decline; instead, he channeled it into the character with a dignity that startled critics. When the film aired, many viewers noted that Gleason seemed “different” — older, slower, but somehow deeper.