I've been doing some research on Susan's green archery dress from The Chronicles of Narnia, and
Narniaweb's analysis of said costume describes the smock/underdress as
"The pale green underdress sometimes acts as lining and sometimes as a completely separate garment.
In the first scenes in which she wears it (when Peter kills Maugrim), the rounded underdress neckline is a full 1" higher all around than the overdress. In other scenes however it shifts, sometimes falling even with the overdress neckline. This makes it seem like a separate piece
From the sleeves however we can clearly see that the same fabric is bag-lined at the wrists. It would seem it is sewn in place at the sleeves, but no place else. The underdress is full-length, just a few inches shorter than the overdress."
which to me sounded utterly retarded. It just makes no sense, especially if you consider the obvious german renaissance influences. However, Lucy's blue dress was made with the same basic look, her sleeves are also lined, but they're more bell-shaped, and when they fall back, you can clearly see the long sleeves of her smock underneath. I just looked at another hi-res photo of Susan and Lucy, and it's as I thought--Susan's is exactly the same!
http://costumes.narniaweb.com/pevensiesfiles/sulucamp2.jpg