Then I can imagine the one night their son wants to go sleep in bed with mummy and daddy...and the day after at school when he's telling his friends what he saw.

"Last night Mummy and Daddy were playing with the Doctor! Because, you know my Daddy played the Master and they must have been playing again because he was leaning over my Mummy and the Doctor and saying 'you will obey me! With the black gloves and everything!'"