Bad

 I used to be shy. Not any more. But I'm still rather modest and retiring.

I've always thought showing off was not something a gentleman ever did.

But I have a friend who does rather like to display his knowledge and yesterday I encountered him on one of his chosen fields of expertise- the art of the Florentine Renaissance- and demonstrated, none to subtly, that I knew more than he did. Can you identify this painting? I asked- and he couldn't- so I told him what it was.

Bad dog!