The Redcoats in Pirates of the Caribbean
No one would have noticed this little blunder if it wasn't for the history buffs. The British soldiers appeared in the film wearing redcoats, but that specific uniform wasn't put into rotation until the late 1700s. Of course, this movie takes place in the early 1700s, so it wasn't very accurate.
Superman in Man of Steel
Man of Steel was highly awaited as it would be the first Superman movie with modern movie technology. Fans were excited until they noticed one very important thing missing from his uniform... The underwear. The directors decided to toss away the idea of Superman wearing a pair of underpants over his little outfit. Fans weren't impressed.