What are they doing?

Because I am somewhat freaky about putting my son's toys away in their respective places, I've become very familiar with all parts and components of his growing collection as well as what is supposed to go where. On a good day you can find me hunting for the 300th Lego piece after I've counted up to #299 and realized one was still AWOL. That's just me being compulsive. I don't need anyone to tell me that. What I do need is help in figuring out what THIS (look below) means.

For the past three days, after I've straightened them out and put them in their respective places, I come back to find all the firemen re-aligned as the photo shows. Looking down raptly into the container. No rhyme, no reason. If I put them back in their original places and leave for a while, I come back to find them painstakingly reset. Their positions might vary somewhat but they are still looking in. AT WHAT? When I ask, the kid just looks at me with a secret little smile and runs off to play with something else. He's messing with me isn't he?