When A Charlie Brown Christmas made its TV debut 50 years ago this December, few people could have imagined it was destined to be a holiday classic.

The story of young Mr. Brown’s quest to find the true meaning of Christmas while everyone around him—including his dog, Snoopy—is caught up in the season’s commercialism was lucky to get on the air at all.

Even its makers had their doubts. As they prepared to preview it for CBS network executives, both director Bill Melendez and producer Lee Mendelson worried that the half-hour cartoon was too slow-paced to hold viewers’ attention.

“I hoped the network would like it better than we did,” Mendelson says now. “And they didn’t.”

In fact, the executives had a whole list of concerns. They thought the animation was crude, the voices amateurish and the music downright weird. And, truth to tell, they were right on all counts.

The animation was crude, with fewer drawings than the more sophisticated cartoons of the day, in part because the show had to be rushed out in less than six months. The voices were amateurish—real children as opposed to adult actors pretending to be kids, as was usually the case. The score, by jazz pianist Vince Guaraldi, was a bold break from conventional holiday music.

But the execs may have had an even bigger worry. Unlike most Christmas specials, this one actually had some religion in it. Peanuts creator Charles Schulz had insisted on a scene in which the character Linus recites verses from the Bible about the birth of Jesus.

The cartoonist drew the line on some other common TV practices, as well. For example, he insisted the show be made without a laugh track, a standard feature on cartoons in those days. He thought people were smart enough to know whether something was funny or not.

In short, the show had a lot going against it—just like its title character, the perennial loser Charlie Brown.

But when it was broadcast, in a Thursday evening time slot normally occupied by The Munsters, something surprising happened. Close to half the American TV audience tuned in. Most viewers loved it, flaws and all, and the critics did too.

While one TV critic dismissed it as lacking the charm of the Peanuts newspaper comic, others got the message. Time magazine praised it as “unpretentious” and called it “a special that really is special.” The Washington Post pronounced the animation “splendid” and Guaraldi’s music “delightful.”

A Charlie Brown Christmas went on to win the year’s Emmy award for Outstanding Children’s Program. Accepting the trophy, Schulz joked, “Charlie Brown is not used to winning, so we thank you.”

In the half century since, A Charlie Brown Christmas has been on TV at least once every year, and gathering around the set to watch it is now a multigenerational tradition for many families. A little ironically, perhaps, it has become a commercial force in its own right, inspiring all manner of holiday merchandise, including replicas of the scrawny little tree Charlie Brown brings home in the story. This October it achieved immortality of another kind, honored with a set of “forever” postage stamps.

The Peanuts gang went on to appear in 44 more TV specials, so far, as well as full-length films, including The Peanuts Movie, out Nov. 6. Mendelson, who has been involved in many of those productions, still marvels at the show’s enduring appeal and credits the quiet but determined genius of Charles Schulz for getting it right.

As he told Parade, “Mr. Schulz knew what he was doing, fortunately, whether we did or not.”

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