Could be that one, mayrock.
Which reminds me. Before Dead Ringers and Greenaway's (1986) film, there were the dueling good and evil brothers in Cronenberg's Scanners (1981); and before that, De Palma's Sisters (1973) featuring twin girls, one good, one evil, a noteworthy influence on Cronenberg that he has rarely, if ever, acknowledged.
In Sisters, the apartment is painted womb red, to dramatize a landscape of female crisis. In Dead Ringers, Cronenberg opts for amniotic blue, to simulate a foreboding sense of being submerged in a fish tank.
It's interesting to ponder how fashions come and go in cinema
Other films in which the same actor plays two different characters: Anthony Perkins in Psycho, Michael Caine in De Palma's Dressed to Kill, the Sam character in De Palma's Body Double.
Films in which a pair of actors portray a single character - Sisters (1973) again, That Obscure Object of Desire, The Return of Martin Guerre, Despair, Lost Highway.
Ola yia tin epistimi!
Dead Ringer with Bette Davis...
A Stolen Life with Bette Davis.
(i thought that Margot Kidder played both sisters in Sisters)
Swing away, Merrill....Merrill, swing away...
There is a scene in Sisters showing the twins as conjoined (a nightmare sequence, I believe) in which a girl resembling Kidder plays one of them.
I'm here, Mr. Man, I cannot tell no lie and I'll be right here till the day I die