Why are there two completely different depictions of the Nazgûl and their flying mounts in the cartoon version of The Return of the King?

Question

The Rankin-Bass cartoon versions of The Hobbit and The Return of the King have not generally enjoyed strong reputations among Tolkien's fans. However, comparing them to some of the live action films, I think they come off pretty well (especially The Hobbit, which is lighter in tone and consequently works better as a children's cartoon); in particular, watching them as adults, it is quite evident that the films were made by people with real admiration for Tolkien's vision. There are a lot of subtle details that come directly from the books, but which the films don't really draw attention to.

However, something that puzzled me many years ago, happened to occur to me again this afternoon. The two face-offs against the Lord of the Nazgûl (first with Gandalf at the breaking of the gates, then Éowyn and Merry) are major turning points in the plot—as they are in the novel. The Black Captain of Mordor is depicted very much the way he is described in the book, and so is his fell mount. (Note the two glowing red eye spots in the Ringwraith's otherwise absent face.)

However, there is also a completely different version of the Nazgûl that appear at other points in the cartoon. They look like corpses mounted on winged horses—not at all like their appearance in the novel.

My question is simple: Why? Were there two incompatible character designs that were for some reason never harmonized and both ended up getting animated? Or was this an intentional decision to show the Ringwraiths and their steeds in two very different ways? And if so, what was the reasoning behind that peculiar creative decision?

Answer 1

I don’t know why the animation does this, but the second character design seems pretty accurate to me, to how they are described when Frodo is wearing The One Ring. (For the Nazgûl themselves, the mounts are never winged horses)

When Frodo puts on the ring at Weathertop, the Nazgûl are described as having visible faces and hair, much like the second picture.

In their white faces burned keen and merciless eyes; under their mantles were long grey robes; upon their grey hairs were helms of silver; in their haggard hands were swords of steel.

The third was taller than the others: his hair was long and gleaming and on his helm was a crown. In one hand he held a long sword, and in the other a knife; both the knife and the hand that held it glowed with a pale light.

_{The Fellowship of the Ring, Chapter 11: A Knife in the Dark (emphasis added)}

The second quote there is explicitly the Witch-King (aka The Lord of the Nazgûl).

But then the description at the battle of Pelennor Fields, when the Witch-King is seen in daylight by characters not wearing the ring, matches the first picture:

Upon it sat a shape, black-mantled, huge and threatening. A crown of steel he bore, but between rim and robe naught was there to see, save only a deadly gleam of eyes: the Lord of the Nazgûl.

_{The Return of the King, Chapter 6: The Battle of the Pelennor Fields}