Working On The Railroad???

I'm bushed after a long work day so it took me a full minute of scrutinizing the photo to get it. Gee, most of the train crews I see just wave (with their hands)! :) Some reader out there must have be thinking up a joke about multiple units or something about the rear being at the head of the train... My brain isn't coming up with it though. Punsters?
Ralph
 
Well, I have to say I never mooned a railfan.......I did get mooned by another engineer who was in a siding waiting for me to clear up.......as for the picture......just a couple guys having fun.
 
Imagine the puzzled look on the faces of the next shift's crew... They'd be wondering what the hell is that wierd-shaped smear on the windshield... And why does it smell funny. sign1