Show us your unexpected moment... the times when you were just at the right place at the right time, and unexpectedly you knew then and there that you absolutely had to take that shot. It could be a time where you just turned around and saw something unexpectedly... or it could be one of those time where you just saw something out of the corner of your eye and you saw a a great photo.
and please, share your story
Here is my story
I live 50 km from Tokyo. One day I went to Harujyuku to shoot the wild youth there... well I didn't get any good pictures there, and it was getting late. I took the Chuo Line to go to Okatchimachi to see my friends, and I had to transfer at Kanda Station. When I was walking up the stares I see this woman standing there waiting to get on the train... and I knew I absolutely had to take her picture. The lighting, the contrast.. everything was just so right... It was just one of those moments...
then she got on the train and left..

http://www.pbase.com/jyoushikousei16/image/71833398
now, please, share your unexpected photo moments