The Flintstones c. 1960 : Unaired pilot from 1959

After a single unaired pilot episode product in 1959 that was approximately 90 seconds long, The Flintstones became an American television sitcom prime-time broadcast from 1960 to 1966 on ABC television network.

https://www.firstversions.com/2015/08/the-flintstones-cartoon.html

Though cartoons were considered children’s entertainment in the ’50s, William Hanna and Joseph Barbera’s The Huckleberry Hound Show, featuring characters like the titular pooch and Yogi Bear, became a surprise hit with adult audiences, who would even go to bars to watch the show. This surprise success inspired the duo, who had already produced Academy Award–winning Tom and Jerry shorts for MGM, to create a groundbreaking adult-oriented cartoon series for prime-time TV.

The Flintstones was not an instant hit, at least not with critics, but the show quickly grew an audience as it married the tropes and humor of beloved live-action sitcoms like The Honeymooners (which Hanna considered the funniest show at the time) with the kind of visual gags you could only achieve with animation. Hanna-Barbera even hired two of The Honeymooners’ writers, Herbert Finn and Sydney Zelinka, to bring the adult humor that was cracking up audiences in the live-action format to the modern Stone Age world of The Flintstones. The cartoon was the first to include laugh tracks and focus on family issues that got resolved with laughter by the end of each episode, and it would create the template for animated sitcoms that The Simpsons ran with decades later to become an animation juggernaut.

The Flintstones, like most of Hanna-Barbera’s productions, made use of looping “limited animation.” The animators kept characters’ hands at their sides. They looped animation of Fred’s feet as he served as the motor of his own car. Characters passed across the same backgrounds over and over again. Limited animation was pioneered by the UPA studio as a stylistic alternative to the more detailed realism of Disney and Warner Bros., but it was Hanna-Barbera that saw the technique’s potential to save serious time and money. The Simpsons memorably mocked this in later years, but in the ’60s and ’70s, this helped Hanna-Barbera become so efficient at churning out shows that 60 Minutes once referred to the studio as “the General Motors of animation.”

https://www.vulture.com/article/most-influential-best-scenes-animation-history.html