Here's a helpful tip for those of us (like myself) who are too lazy to make cake filling: Pudding Snacks!
They come in all sorts of favors. Two pudding cups work perfect for an 8"or 9" cake. Yummy and easy.
**I used fat-free Boston cream pudding and it didn't work out at all...the cake just absorbed it. Weird. But the regular ones worked just great. **