Blackadder does not sport a beard in this season of the show because Rowan Atkinson's then-girlfriend hated it.
Though this series is notable for its historical inaccuracies, Hugh Laurie's portrayal of Prince George (later George IV) is fairly close to the mark. Prince George was made regent in the absence of his father (George III) and was immediately hated by his people. He reportedly lived only for pleasure and didn't care about the public who through taxes had to foot the bill. This also explains the otherwise incongruous references in this series to George (played by a noticeably slender actor) having a weight problem - in reality the prince regent's indulgent life style resulted in him being obese. However, he probably wasn't quite as hopelessly stupid as portrayed in the script.
Tim McInnerny decided to discontinue the role of Lord Percy for fear of being typecast as an idiot; however he appeared in a guest role in Nob and Nobility (1987).
This was the only series of Blackadder where Rik Mayall doesn't appear. This was due to a falling out between Mayall and co-writer Ben Elton, after they had creative differences on Filthy Rich and Cat Flap.
This series of Blackadder marked a change in the traditional line-up of characters. The two previous series, Blackadder (1982) and Blackadder II (1986) included different historical incarnations of Edmund Blackadder (Rowan Atkinson), Baldrick (Tony Robinson) and Lord Percy (Tim McInnerny). This time round the character of Lord Percy wasn't in at all, his role as the foppish fool of the group being replaced by the character of George, Prince Of Wales, the Prince Regent. McInnerny was actually offered the part of George but turned it down as he feared that he would become typecast. He did appear in Nob and Nobility (1987), playing Lord Topper the Fop. Hugh Laurie eventually got the part of George, having played two characters in the previous series (Simon Partridge in Beer (1986) and Prince Ludwig in Chains (1986).