Best Friend is the theme song Harry Nilsson wrote and recorded for the television series "The Courtship of Eddie's Father."

 

The song has been used in scenes in a number of TV shows such as "The Nanny" and was parodied in "South Park."

 

In 2002, the song was used in a public-service ad called "Big Daddy." And, in 2005, "Best Friend" was used in a commercial for the HBO TV Series "The Sopranos."