A tutorial in passive aggression

I received the following email from my boss this morning (names have been changed):

Hi all:

I was very excited to see that there was a plate of chicken dinner on my desk when I came in this morning.  =-O   Too bad I was in the mood for breakfast and too bad it was only remnants.  :-(

I am sure there is a story behind this and I would love to hear it! 

Joy