When Pancks scans a page of Mr. Chivery's book at the Marshalsea, looking for information on Mr. Dorrit, one can see that the entry directly above William Dorrit's is that of John Dickens. Dickens was the father of Charles Dickens and an inmate of the Marshalsea Debtors' Prison for a few months in the 1820s. Besides the imprisonment date, John Dickens' year of birth was also altered.
Emma Pierson (Fanny Dorrit) & James Fleet (Frederick Dorrit) also worked on episode 2.4, Death in the Clinic (2013), of Death in Paradise (2011) as Anna Jones & Jeremy Tipping respectively.