There Will Be Blood (2007)
Daniel Day-Lewis plays a miner-turned-oil magnate in There Will Be Blood. Fortunately, the only thing wrong with his performance had to do with his footwear, not his acting. Day-Lewis can be seen with waffle sole boots even though the movie takes place in the late 1800s; waffle soles weren't invented until the 1970s by Nike.
Ben Hur (1959)
Charles Heston was unaware that the Star of David he bore in Ben Hur wasn't actually authentic. In fact, the first record of the Star of David having been associated with Judaism was in the 12th century; the six-pointed star has no biblical or Talmudic authority.