I made this guitar cake for our neighbor's 7 year old daughter (my 5 year old's best friend). I researched so many cakes and Hannah Montana products until I finally came up with the final design.
I do not have a guitar pan. To begin, I taped together 5 sheets of paper and tried to draw the guitar many different ways with circular pans. It is possible but is very complicated, with a lot of cuts and pastes. After searching my cupboards, I came upon a bunny head pan (guitar body), a loaf pan (top), and 2 individual (mini) loaf pans (neck). I traced the pans to form the guitar and then designed and colored the drawing.
The body of the guitar is white cake, and the rest is chocolate, but any variety works. Two regular, or one doubled, cake recipes are enough. They leave a little extra cake for mishaps. If you are pressed for time, use two boxed cake mixes. I also split the cakes and put strawberry jam in the middle.
The bunny head was the perfect size. I had to trim all of the loaf pans to flatten them, and cut the bigger loaf in half to get the correct size for the top.
The circle was made by placing a 1/2 cup measuring cup into the frosting, and filling the circle in with butterfly sprinkles. For "straight" strings, use a ruler of any long item (I used a wire rack) to indent the frosting for your guide. I recommend doing the strings last. To give the girly glitter look to the cake, I sprinkled white sugar sparkles all over the cake before decorating.
Colors: Many Hannah Montana cakes have pink and blue decorations, and most of her products are lavender. I used Wilton gels to make the colors, and combined the leftover frosting to make the darker purple for the top and bottom edging.
After decorating, lollipops were used as the string tuners, dum-dum size. I also placed a baby food jar bouquet of the remaining lollipops for the rest of the kids at the party, as six was not enough. Then I placed two star lip glosses on the cake, and the bag of Hannah Montana treats where I would have put the logo.
The only unfortunate part about this cake was that I ran out of time and was unable to create the logo on the cake or board. Here's what I was going to do: pipe the logo and sprinkle with yellow and purple colored sugar to give it the "glitter" effect.