I've heard a lot about this. I'm making a french vanilla cake. Do I just add an extra egg and vanilla pudding mix? Anything else? Also I was thinking of doing a lemon buttercream frosting? any other good ideas for frosting or filling? There will be lots of kids so I want something they will like.

This might help:

Info on WASC cake and variations, doctoring cake mixes, all extender & enhancer recipes and more.

http://forum.cakecentral.com/cake-decorating-ftopict-207351-.html

http://tinyurl.com/2cu8s4

To make a French Vanilla cake using WASC directions - omit almond extract, use DH French Vanilla cake mix and six whole eggs not eight egg whites.

Lemon cake, frosting & filling:

http://forum.cakecentral.com/cake-decorating-ftopict-139441-.html

HTH