Character mistake: After firing Percy and Baldrick, Edmund says to Baldrick that he'll probably go back to shovelling dung in the gutter where Edmund found him. In the pilot episode The Foretelling, Edmund actually met Baldrick when Baldrick was pouring a drink for Edmund.
Plot hole: In 'The Foretelling', it is said that Richard IV reigned for "13 glorious years" with a caption showing 1485-1498. 'The Black Seal' starts on St. Junipers' Day, 1498, but Blackadder spends 12 months locked up with Mad Gerald. So when the Royal Family are finally murdered it is actually 1499.
Blackadder: We are reprieved. It is a triumph for stupidity over common sense.
Baldrick: Thank you very much.
Blackadder: As a special reward, Baldrick, take a short holiday. [Pauses for a second.] Did you enjoy it?
Trivia: Stephen Fry, who played Lord Wellington, ad-libbed most of his lines.
Question: Many times during the series, Lieutenant is pronounced as 'Left-tenant'. Why?