ok my DD bday is next week and I 'm making her a Ariel cake she wants chocolate and vanilla cake and I always do BC through out but I thought I would try smething different. Anyone have any suggestions what kind of filling to use and how to do it? I have never used fillings before so this will be interesting. Thank you in advance

If you are looking for easy, then the sleeved fillings are the way to go.
If you have access to Bettercream, then mixing it with any flavor of instant pudding and some milk makes AWESOME fillings and is still easy.

In either case, put a dam of icing around the edge of the bottom layer to keep the filling in. You can use a coupler without any tip for this.

Hope that helps!

I love to fill cakes with whipped chocolate ganache...I use semi-sweet chocolate so that it is not bitter. Easy and wonderful! There are several recipes for it here on CC.

If you like the buttercream normally, how about making oreo buttercream.
Its very easy.
Buy some oreos, they can even be store brand...throw a bunch in a bag and smash them with your rolling pin (my kids LOVE helping with this part).
Then you can either stir them directly into your buttercream, or spread on your BC then sprinkle the oreos over top, add your next layer of cake, etc.

The oreos will soften a bit but this makes them blend very well with most flavors of cake!
Adults and kids both will enjoy this.

wow thank you for all the ideas. The whipped chocolate ganach sounds yummy so does the oreos. I will have to go through the recipes on here and see what I can find. Thank you everyone

I thought I would also let you guys know I found a recipe on CC for cookie dough filling/frosting havent tried it but going to today. will let you know how it turns out

The chocolate chip cookie dough icing/filling is DELICIOUS!!! I'm going to use it on my DD 8th bday cake as a filling for chocolate/ vanilla cake. I make a 2 layer 11x15 sheet cake one layer chocolate and one vanilla so I think this will go great together....