Walk Hard: The Dewey Cox Story

Revealing mistake: When Dewey is singing the protest song about midgets in 1966, modern cars can be seen driving in the background.

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Revealing mistake: When the black singer of the band of the nightclub can't perform, Dewey steps up to prove his worth. When he starts getting really into it, he joins the piano player in playing some tunes. You can see some keys playing, but they are not being touched by either person.