The closest I've come to that feeling is when I had a nice shot of a pair of roosting GBHs all lined up, and a grackle just flew up and landed right in the scene. Can you bird photographers relate?

I've gone to a couple of weddings where I brought my camera, and I tried very hard to not be 'that guy'. I introduced myself to the hired photographers, told them I'd stay out of the way but to tell me if I wasn't, shot ambient, etc.