Lewis also mangles the Incarnation. Aslan is not a lion like all lions in all things but sin. His lionhood is created ex nihilo prior to the creation of Narnia's world. (No wonder it’s never Christmas.)
Aslan is depicted as a true lion (albeit one with superpowers), but it isn't a union of the Divine nature with a particularly beloved created nature. Aslan does flatter a lion he de-statues at the White Witch's castle by referring to "us lions," but for the most part he's just not that into lionkind.
So why, in the logic of Narnia, did the Second Person of the Trinity become a lion? We know the true reason: Lewis thought, correctly, it would make an interesting and appealing story. But if the artistic reason is evident, and sound, the theological reason is absent. The lion of Judah, yes, and the king of beasts, and not a tame lion; that's good enough reason for a writer make him a lion rather than a gopher or an egret, but it doesn't really touch on why God would become anything at all. Functionally speaking, the purpose of Aslan's incarnation appears to be little more than to provide God with a lion-suit to go about meddling in Narnia's affairs.
Come now, you say, lion-suit? Indeed, I say, lion-suit. In addition to the lack of evident reason for an incarnation in the world of Narnia, there is Aslan's temporary appearance as a lamb at the end of The Voyage of the Dawn Treader, which some see as a mark of Lewis's theological insight but I see as a sign he doesn't take the Incarnation quite seriously enough. And finally, in the last paragraph of The Last Battle, we have:
And as He spoke He no longer looked to them like a lion; but the things that began to happen after that were so great and beautiful that I cannot write them.
Now, no doubt the things that begin to happen in heaven are too great and beautiful to be written, but if Aslan ceases to be a lion, then he never was a lion, which as I say is a mangling of the Incarnation.
It can be argued that I'm holding Lewis to an unreasonable standard, that there's no reason an incarnation of the Second Person of the Trinity in some other world need be like His incarnation in ours. That may be true, as far as I know, but that leaves me wondering what the point of it is, then. If what happens in Narnia is radically different than what happened in real life, if Lewis does not intend his made up story to be one in which the Divine Nature is hypostatically joined to a created nature, then what did he intend? (Yes, a fairy tale. Then why do some insist that this fairy tale is perfectly sound theologically?)