I am No Sure Why any one wants to Take On Glen Campbell after All These Years, But Some People are Just That Way !
Duke Himself ask Glen to be in The Film and at this time Duke Got What He Wanted !!
And Why Would They Have Glen Campbell do the Theme Song for The Film if Hathaway Hated Him That Much and then Put His Name On The Film ?
Below will show You What Glen Campbell had to Say about being in The Film, and then Sings The Theme Song !!!
Chilibill 
