D&D does dystopian children's fantasy: Looking for some ideas

Hey ho, so I'm taking over running one of my existing D&D groups. I have a campaign in my pocket that I have run part of before, A dystopian Narnia. If somehow my players meet just the right overlaps of nerd and techness to have ended up here. Leave now .

But it's really a set up for a longer campaign that I hope bridges into more worlds. I have the Narnian World really fleshed out, but if somebody feels particularly passionate and has ideas, please let me know. I can provide any detail folks would like into being asked a tricky question just helps me World build so please go for it.

The general gist is that our adventurers are pulled by a much weakened aslan from faerun or whatever default world we start from into Narnia. There they find it has been a thousand years of winter and rule by The White Witch. I'm familiar enough with the lore that if they decide to leave the country of Narnia or seek out another witch as an ally I have some options. Hopefully they save the day and free Narnia from Christmas-less winter. (I'm leaning hard into all the broad references to mythology in Narnia, Dionysus and the Maenads, the River God

If they do, they will receive a set of the magic rings used in The magician's nephew to allow people to pop between Narnia and the wood between the worlds. Allowing them to hop into other stories that have been similarly messed up.

I am looking for One Big Idea But also some other suggestions

1. The suggestions I'm looking for are other stories from about the same realm of stories that could be similarly messed up, ideas I had included Dinotopia, Wrinkle in Time, The Rats of NIMH, maybe one of the Discworld stories (I feel like half of those characters would be self aware) particularly thinking middle grade books with a dip towards children's or younger YA stuff, particularly fantasy stories, particularly those with some nostalgia for my fellow millennial PCs. I don't want to touch Harry Potter.

2. My idea for the reason why the story went wrong is that someone is rewriting it, possibly due to hating children or hating happy endings or something. I wanted a BBEG but I can't think of one. Umbridge is out for the Harry Potter reasons, but who else would go to the trouble? I am planning on the villain having acquired "magical book mcguffin" (that I also need to figure out) that's letting them do this. I like the idea of a villain who gets a lot of power but uses it in such a petty way, to rewrite children's stories

It'll take a long time to get out of Narnia, we don't play very often, and we may not continue depending on how players feel but as someone who's worked this idea over and over in their head for a while, I would love to get past these things.