michael j. fox-2 , whose clone-father had starred in the back to the future films plus mars attacks and clone high , took the role of replicant leon kowalski , and dina meyer-2 , whose clone-mother had starred in starship troopers and johnny mnemonic , took the role of the opera-singing replicant luba luft from the book , having barebots replace her vocal cords with synthetic ones just for the role .