Iago seeks revenge on Othello, in part, because Othello makes Cassio his second in command. Iago is played in this film by Kenneth Branagh, whose mentor, Derek Jacobi, made his debut as Cassio in Othello.
José Ferrer first made a name for himself by playing Iago in a theatrical production of Othello, before taking on his most famous role of Cyrano de Bergerac. Iago is played in this film by Kenneth Branagh, who also went on to play Cyrano on BBC Radio.