Random Dyanmic Masking

I am trying to create a ripple effect. I have a movie that uses dynamic masking, but I would like to have it appear randomly, with more than 1 instance.

Basically there is an image, and the effect I am trying to create is a ripple, that appears randomly, and more than 1 time.

Anyone have an idea how I could use the dynamic masking and have it display randomly?