Apparently (this isn't spoilery for the episode, as the context, alas, means it won't be broadcast), Brooker at one point, whilst relaying instructions from the voice in his ear to Mitchell, said, 'You want me to take off his what? Kiss him tenderly?'

So, hypothetically, if I were interested in fic on the subject, would there be any where Brooker says this and then starts following the instructions in the earpiece, and David Mitchell is sort of worried and pleased and confused and alarmed all at once, and Brooker goes "Don't blame me", taps his earpiece, and grins?

Hawes claimed that she was releasing her own fragrance, named 'Dave' after her son's imaginary friend. Mack made the connection with David Mitchell.

Now I want David Mitchell to actually be the imaginary friend of Keeley Hawes's son, and for her to not be telling him he's imaginary for fear he'll vanish into a puff of logic.

Erm, possibly in fic form. It might be unduly complicated if that were the case in real life.