Dogs like to make their own fun; Usually by rolling in stuff. Those stupid, silly canines will roll in pretty much anything. It can be disgustingly adorable.
Just hose them off before letting them back in the house (Trust me on this.).
*I got the idea for this after my roommate friend's son said, "I'm rolling in my own fun!" while playing a video game, making his character repeatedly roll around. We have no idea what he meant by it, but it was hilarious non-the-less.