Keeping with my birthday tradition, the cake inside was my all-time favorite cake: pineapple upside down cake. Mine is never quite as good as my mother's version, and I improvised a little and made the pineapple upside down part a substitute for filling. I was worried that the fondant would not sit quite right without a buttercream crumb coat, which would be a weird addition to a pineapple upside down cake, but with enough smoothing everything turned out just fine.
At Jessica's recommendation I used modeling chocolate for the stripes, and it really was the perfect medium - the time it took to cut all the stripes would simply not have worked using fondant or gum paste. I think modeling chocolate might be my new favorite thing to decorate with. The only problem I had was figuring out how to color it correctly. (Similar to fondant) the modeling chocolate only takes so much color. I was hoping for navy stripes (notice the gold "cord" at the base of the cake - I was going for sort of a nautical feel) and so I started with black chocolate, thinking it better to end up darker than with a pastel blue. I added a TON of blue color to the black chocolate, and thought I'd eventually achieved a navy blue, but in the end it just turned out black. I'm still really happy with how it turned out.