Elvis Presley remains an unmatched American icon, especially in his 1964 film Viva Las Vegas, where his chemistry with Ann-Margret lit up the screen. Their duet, “The Lady Loves Me,” is memorable, but behind the scenes, some funny mistakes and bloopers went unnoticed—until now. Viva Las Vegas became Elvis’s highest-grossing film, despite mixed reviews. Elvis stars as Lucky Jackson, a…