Moffat choosing Sherlock's cast:

Moffat: we need someone to play John's wife.

Moffat: wait...Martin has a partner.

Moffat: but who can we get ot 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.