Probably my favourite cartoon - most amusing.
First: While the animation is of decades ago it achieves a number of magical, unforgettable, moments that spring from the animators' minds, not technology.
Second: Animation usually shines for me most brightly in animal characters (some of Disney's most painful moments have human protagonists) and here all the characters are animals (foxes, lions, a bear, snake, badger, rooster, chicken, dog, mice, elephants, rhinos, crocodile and many more) - all quite believable.
Third: Roger Miller (a minstrel) wrote & sung 3 good songs, one which recurs is quite excellent. Also phony scenes where a couple inexplicably break into song are avoided.
Fourth: Voices. Peter Ustinov, Terry Thomas and Carole Shelley are a luxury.