I woke up early yesterday morning with a sudden thought that I couldn’t figure out the answer to. You know Coronation Street? (If you don’t watch it, stick with me, because it’s a universal soap question really). The character of Bethany (a little girl of about three) is played by twins, so that it’s not too stressful for them, all the long hours and such.
But what happens if the same actors want to continue the part as she grows up… when she’s old enough they’ll only need one person to play Bethany. How do they decide?
It was suggested to me that it could be the reason that child characters always change as they’re growing up - secretly the casting people don’t want to have to choose between twins. I’m not sure I agree with that but I can’t think of any other answer.