Graduation Party Theme Ideas?

I'm throwing a graduation party and i need some ideas. Its going to be formal. I still want everyone to have fun tho so i probably won't do a force-everyone-to-wear-black-and-white theme. I was thinking of something unexpected, like having everyone wear dresses and suits but w/like converse, fedoras, ridiculously oversized sungles, wigs, silly stuff like that. (obviously like 1 or 2 crazy things per person not all together) and having a dessert only party w/a million kinds of desserts. It'd be indoors, probably around late august early october (late i know). What do you think of that idea? Any other suggestions or links would be helpful! Thanks :)