I don't necessarily think that Rillian's appearance has to change, flashback or otherwise, as a means to hold off the fact that the madman tied to the chair is Rillian himself. All that's needed is a bit of doubt and would come down to the performance - give our heroes (and the audience) a sense of doubt, why would Aslan have them free such a madman??? Nothing works more amazingly in a psychological film than to build up a character that seems mentally unstable and then ultimately have them be what they are not or vice-versa - have the audience question what they have seen all along, is it normal or is the character truly insane? - The Yellow Wallpaper anyone?

If it does come down to appearances, couldn't it be argued that Rillian has been prisoner and underground for a long time? Not to mention all that the Lady of the Green Kirtle has done to him. Surely that would change him to almost unrecognizable.

Perhaps, if a flashback is needed for the prince's story, an animated sequence like the tale of the three brothers in The Deathly Hallows, though maybe less jarring. Something like what The Rose-Tree Dryad said, told through stained-glass and tapestries, but have them move in a stylized animation.

That sounds like a good idea, but where would you put these tapestries & stained glass portraits? Certainly not in the Owls' ruined tower. Jill and Eustace could see these tapestries at Cair Paravel, and remember them as the Owls talk, perhaps. And King Caspian might have something about his Dawn Treader return to Narnia with his wife and queen, the gorgeous Liliandil as well.

Sometimes I wonder if the filmmakers are going to try to turn the Lady of the Green Kirtle's true nature into the twist, rather than Rilian's identity.

Obviously, her turning into a snake is quite a surprise, but that's not really what I've got in mind. I'm wondering if they might try to sell the idea that she's a good character—that she really loves Rilian and is trying to help him—so hard and so effectively that the audience is very slow and reluctant to accept the idea that she's the bad guy. "But—she seems so nice! She loves him! There must be some misunderstanding!" A bit reminiscent of that feeling you get when the nice person turns out to be the murderer in those mystery movies.

If they went this route and were able to execute it well, then I think it could potentially make her final scene and her final enchantment all the more riveting for the audience, because they, too, will be somewhat under her spell already.

To be honest, ever since I first read the book I've thought that the notion that the Queen's enchantment over the Prince "wears off" every day and he has to be bound to the Silver Chair to re-establish it, to be a weak plot device. If she was unable to create a permanent hold over him, you would imagine that she wouldn't let him out of her sight for longer than a few hours, in case he broke free from the Chair (even without help from outsiders) and the enchantment wore off completely. And why is the Chair significant? Did it feature in the Queen's initial establishment of the enchantment?

Slightly off-topic, but I just wanted to comment on this. I actually really liked that plot element because, for me, mind-altering enchantments are much more interesting than mind-control. So, I think it's more interesting that, instead of being able to completely overwrite Rilian's true identity and control his actions, she's limited to doing so most of the time, so the enchantment has to be renewed. Also, I don't think she ever does leave him alone for very long at a time--the only time we see him without her, it's in Underworld, with gnome guards under strict orders to bind him to the chair when the hour approaches, and she appeared part-way into that hour. So yes, it's a little convenient that our heroes happen to arrive one of the rare occasions that the Witch isn't there for the appointed hour--though, you could argue that's just as much because it's part of Aslan's plan.

Okay, back to the actual topic!

4) An idea I had would be to have images showing Rilian's backstory during the opening credits. There could be a voice-over, but I think it would be better for the images to speak for themselves. The images themselves could be carvings on a wall (like in Aslan's How), stained glass, a storybook (though this might be too cliche at this point), pictures resembling Pauline Bayne's illustrations etc. Once the opening credits were over, the movie would open with Experiment House and go on from there. The owls could still explain Rilian's story, but they wouldn't have to go as in-depth as they normally would, because the audience will remember the opening credits. That way Rilian's backstory would still be explained visually, but the audience wouldn't recognize Rilian in Underland because he was stylized during the opening credits.

If they're going to try to keep the Knight's identity a secret, I think this is the best route--it's still visually interesting, without having to resort to "trickery" that I think most viewers will see through. Either that or, while Jill and Eustace are hearing the story from the Parliament of Owls, one of them (probably Jill) imagines the story being told, in a very stylized way as to express that this isn't a true flashback. After all, Jill and Eustace find out what the Prince looks like, so it makes sense that as they're imagining him, they don't imagine him correctly.

I don't necessarily think that Rillian's appearance has to change, flashback or otherwise, as a means to hold off the fact that the madman tied to the chair is Rillian himself. All that's needed is a bit of doubt and would come down to the performance - give our heroes (and the audience) a sense of doubt, why would Aslan have them free such a madman??? Nothing works more amazingly in a psychological film than to build up a character that seems mentally unstable and then ultimately have them be what they are not or vice-versa - have the audience question what they have seen all along, is it normal or is the character truly insane? - The Yellow Wallpaper anyone?

I think this route would work even if they don't take pains to hide the fact that the Knight is Rilian. After all, he's been kidnapped, enchanted, and trapped in Underworld for ten years; it's natural to assume that he may, indeed, have lost his mind. And really, I think this is what the book drives for as well; regardless of whether or not you believe he's actually Rilian at that point in the book, the man constantly threatens them, or to cause terrible destruction, if he's released. Like you said, though, it depends on how the scene is handled.

Obviously, her turning into a snake is quite a surprise, but that's not really what I've got in mind. I'm wondering if they might try to sell the idea that she's a good character—that she really loves Rilian and is trying to help him—so hard and so effectively that the audience is very slow and reluctant to accept the idea that she's the bad guy. "But—she seems so nice! She loves him! There must be some misunderstanding!" A bit reminiscent of that feeling you get when the nice person turns out to be the murderer in those mystery movies.

If they went this route and were able to execute it well, then I think it could potentially make her final scene and her final enchantment all the more riveting for the audience, because they, too, will be somewhat under her spell already.

Hmm, I think that could be a really interesting twist on the character, if they handle it well. I would maintain that, in the end, they'd have to confirm that it was all an act--her intentions with him were purely evil, all in the name of conquest. But if they could pull this off, I think it would go well to establishing her as the mysterious, manipulative, and malevolent* witch she is.
(*Okay, I admit I was just having fun with that )

If they can get the audience to believe that she is nice and innocent up to the last little bit, then said audience will probably be more sympathetic to Rilian's plight when they find out. On the other hand, there is plenty of suspense when you sit there on the edge of your seat, inwardly shouting at the protagonist, "No, don't trust her, don't trust her!"

If they could manage to combine the two elements...

Just so long they don't try to make it look like a mistake, like The Wolf's Tale, the Big Bad Wolf's version of The Three Little Pigs.

I would maintain that, in the end, they'd have to confirm that it was all an act--her intentions with him were purely evil, all in the name of conquest.

Oh yes. And then, many years later, we can have the hit Broadway musical Kirtle where she sings a power ballad about defying something and it's revealed that she was just misunderstood all along. I'm just saying, the LotGK and the Wicked Witch both have green going for them....

(Hollywood and Broadway, this is a joke. Don't you dare. )

But yes, I agree. They need to make it clear that she's a bad lady. Although I would imagine that the LotGK turning into a giant serpent and attacking Rilian will probably remove any doubt that she's evil. I don't think many people will be upset when they hack off the serpent's head.

If they can get the audience to believe that she is nice and innocent up to the last little bit, then said audience will probably be more sympathetic to Rilian's plight when they find out. On the other hand, there is plenty of suspense when you sit there on the edge of your seat, inwardly shouting at the protagonist, "No, don't trust her, don't trust her!"

If they could manage to combine the two elements...

I'm thinking that, effectively, it probably would be a happy medium between the two. The audience will be somewhat bewitched by the character of the LotGK for most of the movie, but near the end, when it's revealed that it was she who had bound Rilian to this enchanted chair, and the audience realizes that she had sent them to Harfang with murderous intentions rather than hospitable ones... and finally, when she begins to deny the existence of Narnia and Aslan... that's when the viewers will be inwardly screaming "Don't listen to her!"

One idea that occurred to me was in the scene where Puddleglum & the children meet LotGk & Rillian, what if they set it near a ridge of hills and had the children about half a soccer field away from the hill with Rillian & LotGK riding along the ridge. LotGK sees the children and gallops down, but Rillian stays at the top of the hill. Then the audience's focus is more on the lady and if anything, the knight just looks like some kind of escort, rather than her companion. With luck, people will think he's her accomplice, at least until we meet him in the Underland.
Could that work?

I didn't realize that the black knight was Rilian when we first met him and the LOTGK, but as soon as they were taken by the gnomes and we meet this character I knew it was Rilian. I don't think there is a good way to handle Rilian's identity as suspense, but I remember how stressed I was about them destroying the silver chair.
If I wanted to play up suspense, I would try to make Rilian look more mad and dangerous than I think he comes across in the books. Of course his character works in the book, but Hollywood always wants to make things more dramatic. I guess the best way to describe how I would imagine this insane Rilian is to imagine the scene in Sherlock when Moriarty is shown in Sherlock's mind. Maybe not that extreme, but similar acting.

If I wanted to play up suspense, I would try to make Rilian look more mad and dangerous than I think he comes across in the books. Of course his character works in the book, but Hollywood always wants to make things more dramatic. I guess the best way to describe how I would imagine this insane Rilian is to imagine the scene in Sherlock when Moriarty is shown in Sherlock's mind. Maybe not that extreme, but similar acting.

They tried to do that in the BBC version, but I didn't like it as much as the book Rilian. :C