How to make your own bubble skirt
Kelly Henderson from Harsh Designs gave me this tip at the Degrassi carnival shoot -- if you find a cute vintage or thrift prom dress and want to customize it, you could always turn it into a bubble skirt (kind of like Zoe Saldana's wearing in that picture). Here's how:
1) When you have your dress (probably one that's not already super short), buy a shorter skirt made out of jersey fabric -- a somewhat fitted one, rather than a circle skirt.
2) Then sew the bottoms of the skirts together, gathering the fabric of the outer dress to fit the jersey skirt (somewhat symmetrically -- kind of like pleats, but you don't have to be militant about the measurements). Experiment with pins first to make sure you like how it bubbles out.
3) You just wear the jersey skirt waistline around your waist with the dress over it; the bottom of the outer dress will be pulled into a bubble shape.