Pop singer Nancy Sinatra has a supporting role and performs one song written for the film ; and The Bobby Fuller Four appear as themselves and sing two songs .
Pop singer Nancy Sinatra was on the rise at the time just before the film was released .
Pop singer Nancy Sinatra , who was on the rise at the time just before the film was released , has a supporting role and performs one song written for the film ; and The Bobby Fuller Four appear as themselves and sing two songs .