Calvin and the Colonel (ABC 1961-62), to me, is probably one of my favorite animated sitcoms. Maybe that's not a fair assessment; they literally took old Amos 'n Andy scripts and drew over it with talking animals, but it's a still a great example of a well-written animated sitcom, maybe on-par with the best Simpsons episodes (talk about an odd comparison!).
After its one season run on ABC it entered syndication and stayed there up until the late 1970s. It was also distributed internationally; Japan, for example, aired the show around 1967 as OK! Calvin, while Australia aired it for quite a while, at least until the late 1980s.
Most video copies in circulation came from 16mm black-and-white network prints although somebody is offering DVDs of episodes in color (I'm guessing it was transferred from the syndication prints).
In the meantime, here's one of the episodes in b&w, Nephew Newton's Fortune (first aired April 21, 1962). Features voices by Freeman Gosden (Colonel), Charles Correll (Calvin), Virginia Gregg (Maggie Belle), Beatrice Kay (Susan), and Paul Frees (Judge Clutch), with June Foray voicing Calvin's ex-fiancee. No clue on who voiced Newton, the doctor, and the taxi driver.
EDIT: Joe Flynn did Newton's voice and Paul Frees did the doctor and the cab driver. In addition, much of the animation was done by Phil Duncan. Thanks to Yowp and Mike Kazaleh for the infos.