I really like the idea in principle, as it could be a great way to expand our the dialogue from the books, whilst also adding greater depth and meaning to the movies themselves.

I guess though I don't have an intimate enough knowledge of CS Lewis other writings (particularly his narrative fictions) to easily think of lines which could be readily transposed from one book to the other.

In terms of his non-fiction writing though, many of his most famous quotes would thematically map quite well into Narnia ("made for another world " etc) however I didn't know which characters could most effectively deliver those lines without ending up sounding overtly like CS Lewis himself.

The professor in LWW already serves as the Lewis surrogate character for that story, and already has plenty of dialogue which mirrors Lewis' own writings, therefore I was thinking that maybe the best place to start would be with the younger Digory in MN.

You would probably need to strip the lines right back down, to avoid it coming across like Digory is a walking-talking CS Lewis quote machine, and to render the dialogue in rougher forms, such that they would seem more like ideas that a child was conceiving of for the first time, but I think it could work well.

Bringing this thread back… There are so many great Lewis quotes that I'd love to see included but for The Magician’s Nephew, ones that immediately come to mind relate to Digory’s grief over his mother. I can easily imagine a moment between Digory and Aslan, during their “grief is great” scene, echoing something like this:

"No one ever told me that grief felt so like fear. I am not afraid, but the sensation is like being afraid. The same fluttering in the stomach, the same restlessness, the yawning. I keep on swallowing." 

"Grief is like a long valley, a winding valley where any bend may reveal a totally new landscape." 

Of course, it would need to be adjusted slightly to feel natural coming from a 10-year-old, but I think it could be incredibly powerful.

It’s okay with me if Greta uses lines from other Narnia books. But I think it should be something that relates directly to the Narnia stories. It’s something that could be put in the story without interrupting its flow. It could give the film more of a feeling like it was inspired by the author’s books.

I don’t have any off the top of my head but I’d be a little wary of pulling too much from outside Narnia directly. Each book already has a distinct voice, and adding lines from Lewis’s other writings could risk making it feel a little… patched together?

Narnia is already full of great lines, I think I’d appreciate it more if Greta just decided to use more of the book’s dialogue or narration in her writing. Lewis has already given her so much great material to work with so I hope she takes full advantage!