So it all started with Janet Jackson's "costume reveal," then Extreme Makeover on ABC started calling the final part of their show the reveal, and finally FOX cememted it my using the "reveal" as the climax of thier everpopular show The Swan.
A reveal is the part of a reality makeover show where you see how not- beat-up the person is.
Susan: Paula looked really beat up before her reveal on The Swan.
The alternative way of describing Janet Jackson and Justin Timerlake's Superbowl 2004 antics. See also "wardrobe malfunction." Costume reveal is perhaps more honest given that it was clear they intended the "reveal," but "wardrobe malfunction" is more fun to use (e.g., "My date last night was terrible - I think he had a wardrobe malfunction").
When Jason was jumping on the trampoline, he wasn't wearing anything other than a speedo, and his business was completely showing. Talk about a costume reveal!