I'm planning on making my friend WASC cupcakes (my first attempt ) for her birthday on April 15 with BC french vanilla using kakeladi's original WASC recipe. The thing though is that I really don't want to use the canned BC frosting and want to make my own. Are there any recipes out there that can be used as a frosting and a filling? Also, I don't want to wake up super early to fill the cupcakes so if I fill and frost them the night before, will the cupcakes still be okay to eat?

By the way, my friend's allergic to blueberries and she's pretty much anti berry except for strawberries so I was thinking of a strawberry frosting that can be used as a filling but are there any other suggestions?

What's the difference between frosting or filling or is it the same thing?

Well... frosting and filling can be the same thing, or they can be different. So I guess that doesn't really answer your question. I think when most people think of fillings, they are referring to something softer that may not be able to pipe on top as a "frosting", such as lemon curd, pastry cream, pudding, etc. Of course, you can fill a cupcake with the same thing you are frosting it with as well.
Depending on what you choose as the frosting and filling, it should be just fine left out over night (perishable fillings will of course need to be refrigerated). In fact, many of my cupcakes are made on the weekend to bring to work Monday morning.
My first filling thought for WASC was raspberry, but if your friend is anti-berry then I guess that wouldn't work! Do you plan to use the almond extract? I often leave out the almond so that my cake flavor is more compatible with other flavors. I really like to fill my chocolate cupcakes with a "Hostess" type filling and cover with a chcolate glaze For a white/vanilla cake you can try a dulce de leche or carmel filling.

I don't plan to use the almond extract but is it necessary to use any extract using the original wasc recipe? Can it just be used as an extender?

I always add an extract, because you're adding a cup of flour and a cup of sugar, which to me just tastes "sweet". You'd be diluting your original mix flavor otherwise. I've never tried it, but all I can say is try it without the extract, taste the batter, and you can add if needed! Good luck

Go to the following post. It is a VERY long post (currently at 116 pages). Please feel free to read everything, but I recommend to start that you fast forward to one of the last pages & look for a post from MACSMOM. She has a link in her signture to a google doc that has a lot of WASC variations, fillings and frostings/icings. While the recipes do not use Kaeladi's WASC recipe, there are rave reviews in that thread for most of the recipes.

http://www.cakecentral.com/cake-decorating-ftopict-614554-.html