In 1986 the world was invited to ring in the New Year with Charlie Brown during the prime-time animated TV special “Happy New Year, Charlie Brown.” Now, three decades later, audiences continue to count down the clock with everyone’s favorite blockhead.

But despite the holiday special becoming an annual tradition for many families, there still might be some things even long-time viewers don’t know about the 30-year-old cartoon created by cartoonist Charles M. Schulz. Check out five facts about the festive TV episode, which is set to air Monday, Dec. 28:

1. Little Red-Haired Girl

“Happy New Year, Charlie Brown” is the second Peanuts’ special where Charlie Brown’s crush, the little red-haired girl, makes her appearance. The first time the redheaded character, named Heather Wold, made her debut was during the 1977 special “It’s Your First, Kiss Charlie Brown.”

2. The Little Red-Haired Girl’s Inspiration

Donna Wold, a former flame of Schulz who sported “violently red” hair, was the inspiration behind the little red-haired girl. According to  Vanity Fair, Wold and Schulz had dated three years before the cartoonist popped the question. Wold, however, declined his marriage proposal and opted to choose a more fitting suitor. This sent Schulz into a fit of despair.

“I can think of no more emotionally damaging loss than to be turned down by someone whom you love very much,” Schulz said years later. “What a bitter blow that is. It is a blow to everything that you are.”

Nearly a decade after their break up, Schulz introduced the little red-headed girl into his comic strip. But, according to Wold, the red headed cartoon's introduction was anything but subtle! Wold revealed she knew the Peanuts newcomer was inspired by her “right off the bat” – especially since Schulz incorporated inside jokes that the two of them shared together in the comic strip.

“It was just like reading an old love letter,” Wold said to Vanity Fair. “It was so very nice to be remembered.”

Happy New Year, Charlie Brown" Facts Peppermint Patty throws a New Year's Eve party for her friends during "Happy New Year, Charlie Brown." Photo: ABC

3. In Loving Memory

The New Year’s special was dedicated to Bernie Gruver, an original animator of the Peanuts cartoon series, who died of pneumonia in 1985 prior to the series’ debut.

4. Rerun’s Quiet Return

Although Lucy and Linus’ younger brother doesn’t have any lines in the New Year’s special, the mute character manages to steal the scene when he and Lucy are attempting to blow up balloons for Peppermint Patty’s holiday party. While prepping for the party, viewers can notice Rerun’s balloons are a bit distorted – taking on a cubicle shape instead of spherical.

5. Rerun’s Odd Name

Rerun's nickname was born out of an argument between the Van Pelt siblings that involved Lucy complaining about getting another brother instead of a sister.

“I thought maybe it would be kind of nice to have a sister. So what happens? I get another brother … a rerun!” she says in the 1972 comic. Her metaphor results in Linus dubbing his baby brother “Rerun.”

"Happy New Year, Charlie Brown" will air Monday, Dec. 28, at 8 p.m. EST on ABC.