While Al Capp's seminal comic strip, L'il Abner, never became an animated series, one of the supporting cast made the transition, and it wasn't very successful.
Hanna-Barbera acquired a license in 1979 to bring the armless, shape-changing Shmoo to television, but by taking him out of his familiar milieu and pairing him with a generic group of amateur crime-solvers, who were also running a small comics company for their primary vocation, they felt required to christen the series, The New Shmoo. Seanmc uploaded the open:
Two months into the season, the series was merged with Fred & Barney Meet The Thing to form the equally ridiculous 90 minute Fred & Barney Meet The Shmoo, but all that did was postpone the inevitable. Shmoo shuffled off the air after 1 season, and the rights lie with either the Capp estate or with WB, as I believe reruns have aired on Boomerang in recent years.
Today, if someone wanted to revive the Shmoo, it would be a CGI series, you can bank on it. And it might work the second time around.