These are what we call the 'YMMV items.' Things that some people find in this work. We call them 'your mileage might vary' because not everyone sees these things in the same way. This starts discussions in the trope lists, a thing we don't want. Please use the discussion page if you'd like to discuss any of these items.
YMMV: Black Adder
The show as a whole has:
Ear Worm: The theme song, in all its incarnations.
Fanon Discontinuity: 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.
Seasonal Rot: Inverted for the most part. The Black Adder is generally felt to be pretty average, Blackadder II awesome, Blackadder the Third a slight step down from the previous series but still very good, and Blackadder Goes Forth the best of all.
The Black Adder has:
Crazy Awesome: King Richard IV. Goes to war just for the hell of it and is implied to have killed several turks with a fruit knife.
Fridge Logic: Prince Ludwig permanently impersonating Queen Elizabeth nicely explains the whole virgin queen thing.
Also, Prince Ludwig is very likely an ancestor of Prince George (George IV) from Blackadder the third. George IV's great grandfather was Georg Ludwig of Germany. Which explains the uncanny resemblance (both are played by Hugh Laurie)
Growing the Beard: According to popular opinion, this is the season where it happened.
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 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 CREEPY end to the season.
Blackadder: You mean they actually rehearse? I thought they just got drunk, stuck on a silly hat and trusted to luck.
Blackadder: Well, you could appoint him a high court judge.
George: Is he qualified?
Blackadder: He's a violent, bigoted, mindless old fool.
George: Sounds a bit overqualified!
Cargo Ship: Lord Sod-off Baldrick has a relationship with his turnip.
Crowning Moment of Funny: Blackadder in "Dual and Duality": "A man may fight for many things: his country, his principles, his friends, the glistening tear on the cheek of a golden child... But personally, I'd mud-wrestle my own mother for a ton of cash, an amusing clock and a sack of French porn!"
Magnificent Bastard: This series's Blackadder is a prime example, certainly the most outright evil and manipulative of the dynasty. The only one who not only doesn't die at the end of his series, but actually achieves his goals. The one in Blackadder: Back & Forth does too, admittedly, but he had a time machine - Blackadder the Third's Blackadder did it with just his cunning and wit.
Ensemble Darkhorse: Lord Flashheart. His role is greatly expanded from his previous incarnation's, but he still only appears in one episode.
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.
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."
Tear Jerker: Highly unusual for a comedy series, but the last episode of Blackadder Goes Forth cannot fail to bring tears to anyone's eyes.
It aired on Remembrance Sunday with no complaints. Such is its power.
It's made all the more heartrending in the audio only version, where, since you can't see them, you have to imagine them going over the top, and as the sad reprise of the main theme is happening, you can hear a line each uttered by a character earlier in the episode; George: "We've had some good times, we've had some damn lovely good laughs.", Baldrick: "I thought it was going to be such fun, too.", Darling: "But sir, I don't want to...", and Blackadder himself: "Good luck, everyone...".