I think "Miss Pearl" is indeed a reference to Janis Joplin. They both shared a manager, Albert Grossman, in the '60s, and her final album was titled Pearl. Also, in the song, there is the line, "I'll marry you to a ball and chain," and "Ball and Chain" happens to be the title of a Janis Joplin song. I don't know who "Mary Lou" is. Maybe Lou Reed? They did hang out together and expressed mutual admiration for each other.
I think "Miss Pearl" is indeed a reference to Janis Joplin. They both shared a manager, Albert Grossman, in the '60s, and her final album was titled Pearl. Also, in the song, there is the line, "I'll marry you to a ball and chain," and "Ball and Chain" happens to be the title of a Janis Joplin song. I don't know who "Mary Lou" is. Maybe Lou Reed? They did hang out together and expressed mutual admiration for each other.