That was the one with the two-headed animals, wasn't it? One head always cheerful, the other always morose. My memory may be playing tricks on me, but I seem to remember it using the same wobbly "boiling" technique made so famous by Roobarb.
Yup, Noah and Nelly in Skylark, to give it its full title, and the Roobarb connection is spot-on, because both series were made by the great Bob Godfrey.