Significance of the House that Jack built

The House that Jack built is an animated man in overalls building a house and then painting its exterior. When the house is finished a cat chases a rat across the front porch. A grandma comes outside saying that this is the house that Jack built and this is the rat that ate the malt that lay in the house that Jack built. This program is sent as part of an e-mail from Donovan who disguises it as an email from Chad.