Wild Wild West
The people in this movie, including Will Smith, are dressed in 1950s fashion despite though the events take place in the 1860s.
Braveheart
Mel Gibson's character wears a kilt, but the events of the movie took place in the 13th century, several hundred years before Scots adopted the garment.
Back to the Future
Just three years after the events portrayed in the movie, the Gibson ES-345 guitar that the lead character in the movie plays was released.