In a 1995 interview, Charles M. Schulz, father of the Peanuts comic strip, recalled his reaction to the first production screening of “A Charlie Brown Christmas.”

“I thought it was a disaster,” Schulz said.

TV viewers thought otherwise. The little animated special, built around an anti-commercialization message and starring the saddest Christmas tree on the lot, scored a huge rating for its Dec. 9, 1965, debut — second in the Nielsens that week only to “Bonanza” — then Emmy and Peabody awards. A holidays-TV classic was born.

ABC will mark the half-century anniversary of the special’s premiere with a music-and-memories hour at 7 p.m. Monday. Kristen Bell hosts “It’s Your 50th Christmas, Charlie Brown,” which will feature performances by Kristen Chenoweth, Sarah McLachlan, Boyz II Men and Pentatonix. The original special will follow at 8 p.m.

Schulz and his production team — animator Bill Melendez and producer Lee Mendelson — never would’ve predicted a five-decade run for their first Peanuts special, or the more than 40 that followed.

“A Charlie Brown Christmas” came together quickly, at the suggestion of sponsor Coca-Cola. Mendelson and Melendez had previously worked with Schulz on an unaired Peanuts documentary. Over a weekend, Schulz drew up the new project’s story outline, which called for the Linus character to read a Bible verse.

“Bill Melendez and I looked at each other and said, ‘There goes our career,’” Mendelson said. “I said, ‘I don’t think we can do that on television with animated characters.’ And (Schulz) said, ‘If we don’t do it, who will?’”

The special broke other TV rules. Children, not the customary adult voice actors, spoke for the characters. The animation was crude, clunky. (“The drawing was so poor,” said Schulz, who died in 2000.) And the special featured a jazzy, bossa nova-flavored soundtrack by San Francisco musician Vince Guaraldi, who had worked with the team on the earlier Peanuts documentary after Mendelson discovered the pianist’s “Cast Your Fate to the Wind” on the radio while driving across the Golden Gate Bridge.

Today, “A Charlie Brown Christmas” seems impossible without Guaraldi’s score, highlights of which include the irresistible “Linus and Lucy” dance-sequence song, “Skating” and “Christmas Time is Here.”

Guaraldi, who died in 1976, scored many more Peanuts specials, as well as the 1969 animated film “A Boy Named Charlie Brown.” Pianist David Benoit, who will perform on Monday’s anniversary-celebration special, has provided Peanuts-TV music in recent decades, as well as music for the current feature “The Peanuts Movie” (for which New Orleans’ Troy “Trombone Shorty” Andrews’ horn provides the “wah-wah” sounds of adult speech.)

“‘Linus and Lucy,’ there’s something about it,” Benoit said. “Whenever I play it in concert, people get up and want to dance.”

Derrick Bang, who wrote the 2012 biography, “Vince Guaraldi at the Piano,” said Guaraldi’s Peanuts compositions were “happy, friendly, cheerful bossa nova tunes.”

“And they linger, they last,” he added. “You cannot listen to Guaraldi’s original compositions without smiling.”

Contrast that sound with the melancholy tinge that underlies “A Charlie Brown Christmas” — a reflection of the title character’s already well established comic-strip persona — and you’ve got the formula for an unlikely, unexpected, 50-year hit.

“I don’t think anyone would’ve accepted an upbeat, hipper Charlie Brown, any more than they would’ve accepted a sweet-tempered Lucy,” said Charles Solomon, author of the 2012 book “The Art and Making of Peanuts Animation: Celebrating Fifty Years of Television Specials.” “It was already a popular strip, and so not to include that kind of melancholia would’ve been a mistake.”

Like Schulz and his production partners, CBS thought the whole thing was a mistake in the days leading up to the premiere.

“When the show was finished, Bill and I thought we had ruined Charlie Brown, that the show was too slow,” Mendelson said. “We took it to the network and they hated it.

“We thought there would be one broadcast and I would go back to making documentaries.”

Then the Peanuts gang danced to “Linus and Lucy,” that blockhead Charlie Brown picked out the worst Christmas tree ever, and Linus walked to center stage and asked “Lights, please?” before reciting from the Gospel of Luke.