Harry Potter and the Chamber of Secrets - Who Is That?
In the beginning, when Harry finds Dobby, wait for about 3 minutes. After Dobby hits his head on the cupboard, look in the window to the left, he's there for about 5 seconds. And be quick! You will see a man in a black hat, smiling.
I just looked at the movie after reading this (I have it on the DVR for my kids). There is nothing in the window except the reflection of the inside of the room, and later, the silouhette of the house across the street.