If you’ve never worked with fondant before, I suggest you start with a simple cake like this one. The nice thing about fondant is that it takes on the shape of the cake on its own and gives it a professional look without too much effort. I used a Hello Kitty cake pan, but any flat character pan of your choice should work the same way.
Since birthdays are all about surprises, I usually try to incorporate some surprise inside the cake. There’s nothing like that reaction you get when it gets cut open. In this cake I used an easy method to make a zebra stripe effect inside, which usually gets a “Wow, how’d you do that?”