The reference to Bob's similarity to Paul Newman comes from real life mix ups. He mentioned it in his autobiography. Many people who recognized him in public couldn't think of the name Bob Newhart, and the first celebrity name that they said out loud was Paul Newman.
The title is from the movie The Heartbreak Kid (1972) directed by Elaine May, written by Neil Simon, and starring Charles Grodin, Jeannie Berlin, and Cybill Shepherd.