Invisibility was written in the studio, although Laurie went in with the title and the concept. It's told from the viewpoint of a child (hence the simple and sweet melody)....who wishes she was invisible, so she could watch people all she wanted, and even stare, without incurring the wrath of adults.
Laurie was a people-watcher, and used to wish she could sit on the street corner and just watch, and watch, and watch......
Laurie Z. liked to tell this story in concert. She said it was one of the reasons her career choice was so perfect - She got to watch the audience watching her!