This page shows how Samantha and Molly's collections looked originally, and what has changed for the current (2003) catalog. Kirsten's collection has really not been changed, so I didn't add her to this page. Pictures on the left side are from the older catalog and pictures on the right side are from the current catalog. I am not sure when the items changed over, but it was sometime in the 1990's.
Samantha's older cranberry party dress was brighter red and had the little hearts designs in the lace, whereas the newer dress has more of a flower design (thanks to Jeanette for the picture). The gingerbread house is still the same, so is the music box. Her nutcracker doll has changed (it can now bend at the waist so that she can sit down).
Molly's dress from 1986 up until it was changed in the Holiday 1994 catalogue. Her dress is plain green velvet with no buttons. The snowglobe from this collection was very nice with a sturdy wooden bottom. The nutcracker doll was quite simple and made of wood. Molly's flipbook featured Donald Duck.
Click here for an awesome site, the Complete Guide to American Girls Collecting.