Final appearance of Sheridan Smith as Joey Ross.
Debut of Sarah Alexander as Polly Creek.
Two of the character Franklin Tartikoff's own books are shown on a bookshelf beneath two shrunken heads. They are "Cerebral Entropy In The Age Of Fox News" and "Gonorrhoea And Its Role In The Punic Wars".
Sarah Alexander (Polly) is the third actor from 'Coupling' to appear on this show. Her costars, Kate Isitt and Gina Bellman each appeared in one episode each before 'Coupling' debuted.
The title of this episode may have been inspired by the Sherlock Holmes short story "The Adventure of the Engineer's Thumb".