I started this Hanna Montana Birthday Cake with 1/2 sheet cake iced in a light purple. Once it crusted for a few minutes, I took a Viva paper towel, laid it on top of the cake, and ran my hand over it in circles until the icing was very smooth. I added dark purple trim. The headset was sold as a party favor at Wal-mart in the party supply section (it does have a foam earpiece so you would not want to put it in place until the actual party so it would not "soak" up an icing or leave foam pieces stuck to the cake.)
To make the yellow circle "lights" around the edges, I used the round end of a large icing tip to cut them out and then added sparkles to them. For the stars, I used fondant and a star cookie cutter and overlapped the middle one on top. The microphone was made out of my leftover fondant scraps from the yellow and purple. I added black food coloring and rolled a cone shape. Then I made a ball, smashed a little to give it the right shape, and attached the two pieces using water. I used a toothpick to poke holes in the top of the microphone and then used a clean toothpick to scrape out "On" and "Off" on the microphone. I added the on/off button next to the "On" and used a toothpick to make a small indention where it would "slide" back and forth.
The hardest part was the Hannah Montana logo. I just happened to have a set of play-doh ABC toys that I used to make "Hannah". I had some ABC cookie cutters that I used to make Montana. They are two different fonts if you look closely. I had to freehand the "H" and "M". I printed the logo out to copy as I did this. You could probably print it out as a pattern if you did not have the cookie cutters.
I topped the entire cakes with sparkles to make it shine.
I do not like writing on cakes - it is too risky and has to be done in the final steps. Instead, I use store-bought fondant and my cookie cutters. The ones sold with cake supplies are expensive, check in the cooking section of department stores and in the toy section with play-doh to see what you can find.