That's really inspired me to reread it really soon! I hadn't looked at it that way but of course you're right - it just suffuses the books. And I'd forgotten the humour in the books too is beautiful and unexpected.
I've been grumpy about C.S.Lewis because his book on why he converted from atheism left me incomprehending, but yes - his joy in it is what makes it so wonderful to read and so alive.
I must find more of the film versions now. We've watched 3.