"Cloud 9" is our name for Dancing on a Cloud. This is fairly new to weddings. Its an add-on thats been sweeping the country over the last couple of years. It uses dry ice and hot water to create an atmospheric effect that mimics a cloud. It allows the new couple to appear to be dancing on a cloud, or as we like to say "be on Cloud 9".
It is typically only used for the first dance. We (with approval of the client) will use it until we run out of dry ice. So when we are planning the event, we'll ask when else they'd like to use it, if at all.