Trivia: Not a mistake but a little bit of humor in the movie...in one of the flashbacks when they save the women in the carriage from being robbed the long blonde haired man is a professional wrestler that goes by the name of "Edge" from WWF. There is a line in the movie that says, "You seem to have lost your edge."
Trivia: Dimension films infamously pulled some very deceptive marketing in the trailer for "Highlander: Endgame." Much of the footage seen in the original theatrical trailer is a mixture of clips from the prior films and scenes shot exclusively for the trailer that were never meant to be in the final film. This included the trailer explicitly portraying the film as containing sorcery elements (such as the villain being able to duplicate himself and control objects telepathically) and science fiction elements (including Connor and Duncan jumping through some sort-of mechanical "Stargate"-like portal), despite none of these ideas being present in the finished film.