According to Flight of the Conchords, many things Mel says are taken from actual fans of the group. In the documentary "Flight of the Conchords - A Texan Odyssey", we can see one of their fans carrying a photo of Jemaine's lips, which can be seen in the sitcom.
When Sally is breaking up with Jemaine, there is a sign posted on the fence behind her that reads "No Dumping". This is precisely what she is doing to Jemaine.