He was one half of the legendary Hanna-Barbera team, the duo who significantly changed animation. Some say for the better, others say for the worst. I think they did the best they could based upon the circumstances of their day, namely television cannibalizing movie attendance which meant the eight-minute cartoon short was an immediate casualty to save money.
After MGM canned Hanna and his partner, they led the way toward taking advantage of the new medium by scaling back the number of drawings used. In exchange, their cartoons emphasized character interaction and dialog. I know most people roll their eyes at the mention of Hanna-Barbera shows because my generation was exposed to the stuff produced in the Seventies and Eighties, when it was practically cranked out with a Xerox machine. Not to condone what they did but there was a glut of time to fill and the same people who “tsk tsk” the quality would then label H-B fools for letting the opportunity slip by.
However, if you watch the earlier material from the late Fifties through Sixties, then you’ll witness the inspiration for Matt Groening’s Simpsons, the Cartoon Network’s burst of creativity in the Nineties (Dexter’s Lab, Powerpuff Girls), Nickelodeon’s gems (first season of Ren & Stimpy, Spongebob Squarepants, even As Told by Ginger) and obviously Adult Swim, if H-B did anything racier than Wait Until Your Father Gets Home.