My latest acquisition is Tonner's Jessica Rabbit and I just made plaster castings of her feet. Comparing her feet to the ones of Tonner's American Model prompted me to do some more comparisons. I used plaster castings for these as they were easier to photograph. The unit of measurement shown is cm.
The first photo shows the left foot of following dolls (from left to right): American Model (AM), Jessica Rabbit (Athletic Body, AB), Tyler Wentworth (TW). Considering that the TW body is 16" and the AB is 17", the difference in foot size is notable. However, what I found most interesting was that the feet of the AM and AB have exactly the same arch, only the AB feet are about 0.5 cm shorter, making it impossible to use AM shoes on Jessica.
The next photo shows the left foot of the following dolls: Tyler Wentworth (TW), Sybarite (SY), Monster High (MH), Silkstone Barbie (SB). I did this mainly to check how the MH feet differ from the other dolls. TW feet are a lot bigger, which I could see even without this comparison. SY feet are longer and wider, so no luck there either, although the arch is very similar to MH feet. The SB foot is there just to show you that Barbie shoes could not fit MH dolls. Unfortunately, I don't have plaster castings of Hi:Glam doll's feet, so I couldn't include one in this photo. However, at least their boots fit MH dolls.
The last photo is of smaller dolls' feet. The leftmost is of a playline Barbie, next is Silkstone Barbie, and the one on the right is Tonner's Tiny Kitty. All Barbie shoes fit playline Barbies, some fit Silkstones, and none fit Tiny Kitty.