The character you want to duplicate has to be in the scene somewhere. You can move them off screen and have the copy and the mc change before the transition.
INT, BACKGROUNDNAME- DAY
© -0.678 1280 in zone 3 (this is a random number I made up)
&MC stands back right
@COPY becomes MC
#you can add the codes here to change the copies look
@transition fade in
Or you can offer CC again and add the code after the CC. @COPY becomes MC - But, the copy still has to be in the script somewhere.
I hope all this makes sense 