It's like taking the phenomenon of 'Flash Mobbing' and multiplying it by Bukkake.
I saw some Japanese clip on the web where a chick is removing the chain from her bicycle, and is suddenly made the victim of a hit-and-run jizzing. 'Flash Mope' would be the exact same concept, except with an entire 'Mope Squad' instead of just one guy.
Would definitely appeal to your Bukkake and CFNM/Cum on clothes fans, as well as jaded perverts everywhere.