It's rare, but there are some fans who disregard The Black Adder due to how out of step it is with the following incarnations.
A slightly more common viewpoint is that the Blackadder lineage died with Captain Blackadder at the end of Blackadder Goes Forth, and that Blackadder Back & Forth never happened.note (Which would also require disregarding the future timeline seen in Blackadder's Christmas Carol, although that one does leaves open the possibility that what we see is All Just a Dream)
Yet another is that The Stinger at the end of Series 2 never happened, as many fans thought it too contrived, out of character, and just plain not funny, as well as requiring Prince Ludwig to have survived being run through the chest and struck with a hatchet with 16th century medicine.
"Funny Aneurysm" Moment: The first series' first episode opens with a darkly comic depiction of the Battle of Bosworth Field and even has a scene where Edmund takes one look at the fighting and decides to run away, all played for laughs. The final episode also deals with war but plays it completely straight, and this time Blackadder doesn't get away.
Growing the Beard: Most fans prefer the seasons after the Retool. The first season has its laughs, but it's just not as much fun watching a screwball doofus, his moron friend and his clever sidekick as it is watching a wicked snarker and his two moron friends. However, if nothing else, the first season would still be required watching purely on the strength of BRIAN BLESSED's definitively hammy performance (in fact, it's the source of the current image and caption on his page). Incidentally, Blackadder gains a literal beard in the second season, the first one after said Retool.
Seasonal Rot: Inverted for the most part. The Black Adder is generally felt to be pretty average, Blackadder II awesome, Blackadder the Third either slightly better or slightly worse than the previous series (depending on whether or not Blackadder is too much of a Villain Protagonist), and Blackadder Goes Forth the best of all.
Crazy Awesome: King Richard IV. A crazy and over-the-top Blood Knight who goes to war (and sometimes against his allies) just for the hell of it and is implied to have killed several thousand Turks with a fruit knife. Being played by BRIAN BLESSED certainly helps.
Baldrick is the descendent of a long line of Dung Gatherers. Tony Robinson would later learn that there were many different permutations of the Dung Gatherer (called Pure Collectors) profession when he did "Worst Jobs in History" Documentary series (which also meant he actually had to do it), each in a different era no less! Apparently there were a lot of uses for literal shit.
I Am Not Shazam: Inverted. Other characters rarely call Prince Edmund "Blackadder".
They Wasted a Perfectly Good Plot: There is really nothing wrong with the premise of the first season. In fact it can certainly be argued it had more potential than other seasons, since it's actually rather ingenious. The execution left much to be desired; plot elements with potential (the ghost of Richard III following Edmund around and taunting him) were thrown out, while others were sorely underdeveloped (Brian Bloody Blessed as king Richard IV!).
Blackadder II has:
Big-Lipped Alligator Moment: The scene in "Bells" where Blackadder falls in love with "Bob", which suddenly turns into a love song album commercial, for no discernible reason (well, okay, maybe one).
Growing the Beard: According to popular opinion, this is the season where it happened, quite literally. The original Black Adder is beardless, while the Elizabethan version is bearded, as well as more interesting, although Blackadders of the third and fourth installments are also beardless.
Nightmare Fuel: The Stinger to "Chains" more than qualifies. After the credits, we hear a tolling bell and eerie wind noises (from the intro to Elton John's "Funeral for a Friend") as the camera pans over the murdered, wide-eyed bodies of Edmund, Percy, Queenie, Nursie, Baldrick, and Melchett. We then see Queenie there, alive and well, before she turns to the camera, gives a chuckle in a strange voice and says, in the master of disguise Prince Ludwig's voice, "Now this is a disguise I'm really going to enjoy. If I could just get the voice right." A more creepy than funny end to the series.
Magnificent Bastard: The third Blackadder, Edmund Blackadder, is the butler to the idiotic Prince George of Regency England. A roguish cheat who constantly scams money out of his employer, Blackadder is also left with the task of running the country, manipulating the election of his completely idiotic sidekick Baldrick to the House of Commons to vote down a measure harmful to the prince by setting up a Rotten Borough and taking over the position as the only voter as well as the supervisor of elections by murdering his predecessors. When a bet is made for him to one-up the Scarlet Pimpernel, he simply opts to head down to a coffee house and find an aristocrat at the French embassy. When the real Scarlet Pimpernel is about to reveal his treachery, Blackadder promptly murders him and wins a great award from Prince George by claiming to be the true Scarlet Pimpernel. Even in the finale, Blackadder sees Prince George dead when they've switched identities and takes the chance to claim to be the real prince to the insane King George III, gleefully ascending to the throne of England several years later.
Nightmare Fuel: Played for Laughs it may be, but any writer will probably cringe at least a bit at the Life's Work Ruined plot of "Ink and Incapability," and Edmund's panicky attempts at undoing the damage. Subverted when it turns out that the Dictionary was never actually destroyed. Double Subverted when it is revealed that the manuscript of Edmund's novel, however, was.
Blackadder Goes Forth has:
Anvilicious: The show has been criticized by its over-the-top anti-war message.
This is despite the fact, that if you actually watch the season, it's more "anti-war for stupid reasons and while in war don't do stupid things" than "anti-war."
Awesome Ego: Captain Flashheart is an egotistical braggart that views himself greater than God, while being so entertaining about it that he's one of the most memorable and quotable characters in the series.
Critical Dissonance: While fans consider it as the best incarnation, many critics in retrospective have panned its overtly pacifist stance.
Ensemble Dark Horse: Lord Flashheart. His role is greatly expanded from his previous incarnation's, but he still only appears in one episode.
Genius Bonus: Darling is The So-Called Coward if his medal ribbons are taken at face value. The Other Wiki handily lists them as The Military Cross, The Queen's South Africa Medal, The 1914 Star and the French Croix de Guerre. While in real life they were probably just something that the costume department threw on in universe they show that he served in the Second Boer War prior to 1901, presumably as a teen soldier, rejoined the army at the outbreak of The Great War and managed to do something that got him not one but two medals for gallantry in the face of the enemy, (as the Croix de Guerre wasn't instituted until April 1915 he was serving somewhere where he could get shot at until at least the Summer of that year). It's notable that he's more highly decorated than Blackadder himself and it adds another layer of Fridge Horror to the idea that Darling's twitch is the result of PTSD.
Blackadder: Yes, why not? When this madness is finished, perhaps we could go cycling together. Take a trip to the Old Swan at Henley and go for a walk in the woods.
Given that nowadays there's a heightened awareness of hate crimes, Flash shooting the Red Baron in cold blood and then yelling a homophobic insult at his corpse is pretty awkward to watch. Not that it wasn't in character.
In "Captain Cook", Melchett (Stephen Fry) tells George (Hugh Laurie) that his Uncle Bertie sends his regards. Laurie went on to play Bertie Wooster in Jeeves and Wooster, with Fry as Jeeves.
Ho Yay: "Baldrick, I love you. I want to kiss your cherry lips and nibble at your shell-like ears."
Jerkass Woobie: Captain Blackadder to a certain extent, but Captain Darling to a massive extent. He's a hilariously obnoxious Butt Monkey for the first five episodes, but as soon as he starts to realise that he's being sent to his death he becomes a real person, with a life at home, and even someone who loves him. His stoicism at the end is in sharp contrast to his desperate pleading to Melchett that he not be sent to the front.
Blackadder: How are you feeling, Darling?
Darling: Erm — not all that good, Blackadder. Rather hoped I'd get through the whole show. Go back to work at Pratt & Sons. Keep wicket for the Croydon Gentlemen. Marry Doris. [Beat] Made a note in my diary on my way here. Simply says..."Bugger."
Older Than They Think: Much of the anti-war themes, tropes, and character archetypes relating to World War I (or the Great War, if you prefer) are present in the British war comic series written by Pat Mills and drawn by Joe Colquhoun, "Charley's War."
Tough Act to Follow: Part of the reason why a fifth series was never made, as nearly everyone involved realized that there was simply no way they could top the final moments of this series, and that critics would be merciless if they fell short. Sure enough, when Back and Forth was eventually released, one of the primary complaints was that it cheapened the ending of Goes Forth.