Defictionalization: C. Northcote Parkinson (he of Parkinson's Law) wrote a thick, thoroughly researched and realistic biography of Hornblower that could easily be mistaken for being about a real naval hero. Complete with portraits, maps, a family tree, and some plausible extrapolations. For example, Hornblower's first name was really Horace, and a letter released a century after his death reveals he really did kill Captain Sawyer.
Reality Subtext: Commodore was less historically-researched than the others. Instead, it reflects World War II: Russia's tenuous alliance with England and threat from invaders, occupied and/or neutral Baltic/Scandanavian powers, and Britain's tenuous support.
Horatio, 17 years old as of the first film, was played by 25-year-old Ioan Gruffudd.
Same with the then-25 year old Jamie Bamber as 17-year old Archie Kennedy.
Doing It for the Art: The first series was filmed on ships, and it looked awesome. The second series wasn't; but it still looked pretty good. Sadly averted with the third series, which was done carelessly, and it shows, especially compared to the previous cool instalments.
Executive Meddling: The Forrester estate would only let "Mutiny" and "Retribution" film if Archie Kennedy was written out. (Not unreasonably, since his friendship with Horatio was changing Horatio's characterization too drastically from the source.) The writers convinced them to at least let him die on screen. They then pulled a fast one and had Archie perform a Heroic Sacrifice to save Horatio. And the estate couldn't do anything about it.
Fake American: The Irish/English actress Camilla Power as American Betsy Bonaparte.
Fan Community Nickname: Archie's fans call themselves Crumpeteers. note It originated at A&E message board "A Naughty Pellew Fantasy". The nickname then appeared in a piece of fan fic "All About Major E." AKA "All About Lord Edrington" by Karen (AKA SeaSpotRun). It was a tongue-in-cheek questionnaire filled in by Major Edrington who called Archie "a panicky bit of Blonde Crumpet".
Major Côtard was a villainous English "gentleman" once, trying to seduce Marianne Dashwood as Mr Willoughby of Sense and Sensibility.
Maria Mason used to be a beauty and quite a teenage brat — as Miss Lydia Bennet of Pride and Prejudice mini-series adaptation.
Lieutenant Eccleston was once an officer aboard a cool ship and died in the very first episode. On Red Dwarf, he appeared as Toddhunter.
If you look closely in "The Fire Ship," you can see Anderson applying for a promotion in the Royal Navy.
Maester Aemon was once a famous member of the British Admiralty in "The Wrong War."
Hey, lots of guys and one gal who appeared on Sharpe were in Hornblower.
Major Nairn, a British spy master, is dying Captain Keene (Michael Byrne).
Colonel Fletcher is Lieutenant Buckland (Nicholas Jones). Neither has impressive fighting skills compared to the respective hero.
A workers' rights leader and Sharpe's long-lost brother is Gunner Hobbs (Philip Glenister).
Josefina, a Spanish aristocrat and a beauty, is Senora Ortega (Katia Caballero).
Mr Tapling of the diplomatic service is Runciman (Ian McNeice).
Steward James Doughty (Ron Cook) is Napoleon. Boney himself! Holly crap, no wonder sailor Styles hated him so much.
Keep Circulating the Tapes: A&E Network/Meridian never released the show's epic music score, no matter how badly fans begged for it. The best fans can do is to rip the sound from DVDs. There are files to be found on line, but there are some background noises...
Sending Stuff To Save The Show: Hornblower fans (mostly fan girls) organize postcard drives from time to time. Unfortunately to no success, but hope never dies.
What Could Have Been: Paul McGann was cast in the adaptation of Sharpe, but he broke his leg and the role was re-cast. If that hadn't happened, he would have been shooting Sharpe and Mr Bush would have been portrayed by somebody else.
Word of God: According to Jamie Bamber, Archie is the third son of Scottish lord. Given his status as a Composite Character, the majority of his backstory is composed of either the actors' and writers' statements about him, or Fanon.