According to this blog, this is a dress.
And according to the movie, "Just Friends," it's a shirt.
Or, more specifically, a shirt best suited for the night time when you are trying to seduce your formerly fat childhood best friend who is now rich and hot.
*The title of today's post is from a song from the movie. If you haven't seen "Just Friends," you should rent/buy it now. Great holiday flick! And Anna Faris is awesome.