In the "Dear sis" episode of M*A*S*H, the frustrated Catholic chaplain at the military hospital camp near the Korean front lines writes a candid letter to his sister, a nun.

"I'm almost desperate to be useful, sis," writes Father Francis John Patrick Mulcahy. "No one comes to confession. I have no one to grant absolution to, no one to give comfort to, no one who even wants to bend my ear for 10 minutes."

Later, a patient attacks a nurse and slugs the priest. By reflex, Mulcahy -- a former Catholic-school boxing coach -- punches back. The gentle chaplain is despondent afterwards and doubts that he is making a difference.

"I'm Christ's representative," he tells a surgeon. "Suffer the little children to come unto me. Do unto others. ... I'm not supposed to just say that stuff, I'm supposed to do it."

The actor behind this unique character was William Christopher, who from 1972-83 portrayed one of the most sympathetic priests in pop-culture history.

Here's the bottom line, according to Greg Kandra, a 26-year CBS News veteran who now serves as a permanent Catholic deacon in Brooklyn: "For a time, he played the most visible Catholic priest on American television -- arguably the most recognizable man of the cloth since Archbishop Fulton Sheen."

Christopher, 84, died of cancer on December 31 and is survived by his wife of 60 years and their two sons. His M*A*S*H co-stars hailed him as a professional who -- to an unusual degree -- disappeared into this singular role in a show that, in reruns, remains popular with millions.

Alan Alda tweeted: "His kind strength, his grace and gentle humor weren't acted. They were Bill."

Loretta Swit released a statement calling him "TV's quintessential padre" and added: "Our dear Bill and his goodness are a great argument for there being a heaven. … It was the most perfect casting ever known. He was probably responsible for more people coming back to the church."

Few viewers realized that Christopher grew up in a devout Methodist home in Evanston, Ill. He graduated from Wesleyan University, where he learned Greek. His great-grandfather was a circuit-riding Methodist preacher and some family members thought Christopher would be ordained.

"I wish my grandmother had lived to see me play Father Mulcahy. I think it would probably have made her happy in a funny sort of way," Christopher told me in 1983, as he prepared for a M*A*S*H sequel.

To prepare for his signature role, Christopher interviewed priests to "help get the tone right." Finally, he created a Los Angeles-area panel of priests to help him deal with questions about how a Jesuit would have handled some rites, and tricky war-zone issues, in the era before the Second Vatican Council.

The goal was to show respect for the priesthood, while avoiding what he called "embarrassed priest situations and celibacy jokes." It was especially sobering to learn how to handle rushed deathbed confessions and Last Rites.

"I tried to humanize Mulcahy as much as possible, although I knew there was a certain danger there since he is a priest. But I felt there was an even greater danger if we let him turn into a stereotype," he explained.

In the M*A*S*H finale, a shell blast leaves Mulcahy deaf. Struggling with depression, he urgently prays: "Dear Lord, I know there must be a reason for this, but what is it? I answered the call to do your work. I've devoted my life to it, and now, how am I supposed to do it? What good am I now? What good is a deaf priest? I pray to you to help me, and every day I get worse. Are you deaf, too?"

The chaplain faced doubts, but never lost faith and he kept growing. In the classic "Mulcahy's War" episode, he slips away to the front in an attempt to understand the combat experiences of soldiers. He ends up performing an emergency tracheotomy, using a pocketknife and a ballpoint pen.

This is, said Christopher, a "priest who had been to war and and been changed by it -- forever. … What I learned was that all priests are shaped by their experiences. They live for other people. That's the reality I am trying to help viewers understand."