The Children

The Children were basic computer programs that would simulate the children of those saved into the Data Core. There was only one girl model and only one boy model, so there were many copies. Donna Noble and Lee McAvoy had two Children, whom they named Joshua and Ella. More Children could be found in a playground. River Song read bedside stories to two children, as well as CAL herself. (TV: Forest of the Dead)

Behind the scenes
Joshua was played by Alex Midwood and Ella by Eloise Rakic-Platt. Split-screen duplicates of Midwood and Rakic-Platt in the same costumes were also briefly seen playing the copies in Forest of the Dead.