I'm making 2 wonder mold cakes (doll cakes) and cannot for the life of me remember how much batter goes into the pans. Anyone else know??

Use one cake mix per doll.
There are 2 (or more) different sized pans. In one you can use 2 mixes; the other is a bit smaller and only one mix will fit in it w/o overflowing.
With either size pan, you can use one mix with good results.
For most dolls (unless you are using a pic) you will have to make another cake to put under your mold to give you enough height for the dolls legs.
Other people have said they just fill in the gap w/lots of icing.

fyi, if you are using a doctored or scratch cake...
my BC mix makes about 4.5 cups.
for my Cuddly Bear pan I have used the 3D doctored reciped on here and it was about 5.5-6 cups and it just fit (I think 4.5 might have been too little)

I now use WASC variations which is about 6 cups per box.

good luck!