Face/Off: Nicolas Cage and John Travolta
Face/Off is a special case (in so many ways, really) in so far as it doesn't have two actors playing one character, it has two actors playing the same two characters. Confused? Fair enough. (So was John Woo, as far as we can tell.) For the beginning and the end of the film, John Travolta plays uptight, driven-by-the-desire-to-avenge-his-son's-murder government agent Sean Archer, who is dead-set on capturing the elusive super villain Castor Troy, played in the beginning and the end of the film by Nicolas Cage. Well, technically Cage is Castor only in the beginning, as Castor suffers a timely demise before re-assuming Cage's face (don't ask). Anyhow, for the middle section of the film, thanks to a "revolutionary medical technique" (known as "strained credulity") Archer and Troy switch faces, and Travolta and Cage switch roles. Logic mayhem ensues!