These are what we call the 'YMMV items.' Things that some people find in this work. We call them 'your mileage might vary' because not everyone sees these things in the same way. This starts discussions in the trope lists, a thing we don't want. Please use the discussion page if you'd like to discuss any of these items.
YMMV: The Silver Chair
Applicability: The Lady of the Green Kirtle uses genuine secular humanist/Straw Atheist arguments — Aslan is merely suggested in the mind by her cat as is the Sun by her lamp, the upper world is just a pacifying fantasy, etc. — to try and persuade the heroes that there is no Aslan (God) and there is no Narnia (Heaven).
She could also be a counterpart to the devil.
Epileptic Trees: What exactly the Lady of the Green Kirtle is. At first she was said to be another witch along the lines of the White Witch. Then we found out in The Magician's Nephew that the White Witch was the only survivor of a destroyed universe, so the Lady of Green Kirtle couldn't have come from there. So who is she and where did she come from?
Prince Rilian's ranting as he's tied to the chair. It starts with him sadly remembering his life in Narnia, only to notice Jill, Eustace, and Puddleglum and beg them to free him. When they hesitate, he becomes so desperate that he begins shouting increasingly violent threats at them, to the point where he's foaming at the mouth when they do free him. Keep in mind that this has been going on for years, him "waking up" nightly, only to find he can't escape. Consider also that after he's freed, Rilian is generally kind and reasonable. You have to wonder how horrific things were for him to be so desperate to be freed.