Moffat: We need someone to play John’s wife.
Moffat: Wait… Martin has a partner.
Moffat: But who can we get to play Sherlock’s parents?
Moffat: Wait… Benedict has parents.
Moffat: Where are we going to find a child to play young Sherlock?
Moffat: Wait… I have a child.
Moffat: Man I’m good at this.