The credits for pilot episode ("Mrs. Livingston, I Presume") of The Courtship of Eddie's Father include:

 

Music and Lyrics

Written and Sunged by

NILSSON

 

The second episode ("Teachers Pet") changes the credit to:

Songs Written and Sunged by

NILSSON

 

The misspelling persisted until the credits were updated starting with the seventeenth episode of season 1 ("How Do You Know If It's Really Love"):

Theme Written and Sung by

NILSSON