The New Adventures of Huckleberry Finn

edited from wikipedia:
The New Adventures of Huckleberry Finn is an American television series that originally aired on NBC from September 15, 1968, through February 23, 1969. After the show's original run, the series continued to air in reruns as part of The Banana Splits and Friends Show syndication package. During development, William Hanna and Joseph Barbera stated the show was to be the most expensive half hour ever put on television.

I assume it was the excessive cost that led to this only lasting 20 episodes, because it was popular in its time. Even when I saw it regularly as a five-year old on UHF in the 70's, I recognized a unique show. I'm unaware of anything like it that had been done before or since, at least not as a regular series.

All of the episodes are currently available for watching on dailymotion.  But they aren't nearly the same quality as this youtube clip. And yes, that voice is Ted Cassidy (Lurch).