The New Adventures of Huckleberry Finn was Hanna-Barbera's last primetime entry of the 60's, lasting just one season on NBC in 1968, and airing on Sundays, where it was prone to being pre-empted or delayed during football season, airing as it did ahead of The Wonderful World of Disney.
Producer Edward Rosen also worked on the studio's other freshman series for NBC, The Banana Splits Adventure Hour, which sums up his body of work for H-B, as he was long gone by the time they tried live-action again a few years later. The idea behind this show was to use live actors to play the leads, surrounded by animated characters. The central villain, who seemed to be reincarnated in some toon form on a weekly basis, was Injun Joe (Ted Cassidy, ex-The Addams Family, who was now a part of the H-B repertory company as a voice actor.). I dimly remember seeing an episode or two in its original Sunday night configuration, but, looking back, given its poor showing in primetime, it actually belonged on Saturdays. To that end, it was included in a Banana Splits syndicated package a number of years later.
Cartoonsintros uploaded the open:
If memory serves, I believe H-B took another crack at Huck in an all-animated episode of the CBS anthology series, Famous Classic Tales during the 70's. I'll have to check to verify. The non-violence edicts were already in place when this series aired, so we never saw Huck or Tom Sawyer throw a punch, even at an animated foe. Just as well.