CS Lewis was known to be a literary scholar, so he would have been familiar with Aesop's fables.

Although I think Puzzled was manipulate into wearing the lion skin by Shift (a really shifty ape) and the donkey in the Aesop's fables did not. Plus, Puzzle was not as proud.

Though I could see the resemblance.

@col-klink I don't think I'd heard that particular one, but as Aesop's fables and similar stories (often they're so old we don't know their real origin) have been part of so many cultures for something like 2,500 years, I wouldn't be surprised if Lewis knew that story, widely read as he was! He may have been drawing on it consciously, or he may not have been — I doubt we can prove anything, unless there's a statement from him somewhere that that's one thing that inspired him. But I don't know if he ever commented on it. 

Of course, what happens in The Last Battle is different from what happens in that fable, as Jasmine has noticed — Puzzle didn't dress up in the lion's skin willingly, and he wasn't at all proud to be wearing it. But then, Lewis's point in having a donkey dressed in a lion's skin was nothing like the moral point that the fable is making. It's just a trope, if you like, that Lewis may originally have encountered in this fable and adapted for his own use in the final story of Narnia. Again, we don't know, but it's an interesting speculation and certainly not impossible.

That is interesting and certainly a possibility.

Whether related or not, I do think its worth noting that there is a certain ubiquity in the trope of directly contrasting a Lion with a Donkey, presented as two opposing ends of a spectrum, such as in the phrase "Lions Led By Donkeys"

https://en.wikipedia.org/wiki/Lions_led_by_donkeys