It was on this day in 1965 that A Charlie Brown Christmas made its epic premiere on CBS. But this is one Christmas classic that almost never was.

By the 1960s, everyone loved the Peanuts comic series. So much so, Peanuts made the cover of Time Magazine in 1965. An employee of Coca Cola read this issue of Time Magazine and knew exactly who to call to maybe make a Peanuts Christmas movie to happen.

See, this ad executive of Coca Cola had seen a documentary on Charlie Schulz (creator of Peanuts), and called up the filmmaker who made it (Lee Mendelson) to see if Mendelson and Shultz had ever thought of making a Christmas movie. Mendelson straight-up lied and said yes, and the very next day, Mendelson & Schulz cobbled together the now-famous piece of work.

Their initial brainstorming session yielded some thing that would vaguely feature some ice-skating, and a pageant, because both Mendelson and Schulz had messed up their parts in their own school pageants. They also liked the idea of pushing the religious “keep Christ in Christmas” theme.

That was enough for Coca-Cola — a corporation famously big on Christmas (many credit them for the modern-day, red-suited image of Santa) — to commission the duo to make this movie happen. But the resulting movie made some innovative moves. While artists like to break new ground, producers prefer to make money with formulaic, standard moves that yield sure hits.

In a fitting move, when you think about it, the film used child voice actors (very uncommon for animated movies at the time), and the soundtrack was all sophisticated jazz numbers, courtesy of Vince Guaraldi. Charlie Brown seemed a little depressed, and the movie spoke of the over-commercialization of Christmas. The network and producers were worried the stark tone, religious forwardness, and various creative choices, like using no laugh track (laugh tracks were huge in the 1960s), would make the thing a flop.

Instead, their formula for distinguishing Charlie Brown movies from other animated movies proved to be an instant hit with critics. The TV movie won both an Emmy and Peabody Award, and the unconventional style was so unique and beloved, A Charlie Brown Christmas became the first of more than 50 TV movies based on the Peanuts cartoon series.

Today, A Charlie Brown Christmas is officially the longest-running cartoon special in history, having aired every year since its debut in 1965. On the night it premiered — December 9th, 1965 — more than 15 million people tuned in.

Fun fact: the only adult voice in the film is that of Snoopy: Snoopy was voiced by the film’s animator, Bill Melendez.