Princesses, Mermaids, and Rainbows... she's 4!

Madeline wanted a "castle cake just like Malaika's" for her birthday, and I very nearly bought one from QFC, but... we make cakes for everyone else, and Mad has the best time helping, so I started brainstorming. And, then a little closer to her birthday she wanted, "A castle cake with all the princesses, and Ariel and all her sisters. And the ocean."

Yeah, OK. I can do that. Two figurine sets from the Disney Store, brown fondant, sugar cone towers, Wilton white chocolate candy melts, seashell truffles from Trader Joe's, Little Debbie peanut butter sticks "stairs," sugar paste Little Mermaid decorations and letters/numbers, and Nerds for decor, we were done. Well, plus one waffle cone tower, chocolate, vanilla and rainbow cake, and a lot of buttercream. Phew!

Literally the day before I baked the cakes, I stumbled upon a recipe for "Rainbow Cake" online. Now, our rainbow-loving girl really needed that too, so I did it, she helped, and she adored it. Actually, all the kids at the party ate the rainbow ocean pieces, exclusively.
There are $18 worth of princesses and mermaids on the cake, and they were worth every penny (and then some). She plays with them all the time, and they work very well with the kids' treehouse/dollhouse.

It's a good thing I'm not a perfectionist because there were a lot of things about this cake that were so very imperfect, but... that's what gives it character! And, it was delicious, by the way!!
I used Magnolia Bakery's recipe for vanilla buttercream to frost the entire cake - just dyed blue for the water:

Magnolia Bakery's Vanilla Buttercream Frosting

1 c unsalted butter, softened

About 7 c powdered sugar

1/2 c milk

2 sp vanilla

Cream the butter in the bowl of your Kitchenaid mixer, then add 4 cups of the sugar, the milk and vanilla. On the medium speed, beat until smooth and creamy, about 3-5 minutes. Gradually add the remaining sugar, 1 cup at a time, beating well after each addition (about 2 mins.), until the icing is of desired consistency.

Icing can be stored in an airtight container for up to 3 days.