Revealing mistake: After Blackadder accidentally kills Smedly with one of the suicide pills, he starts ranting about how useless Smedly is as a hero, because he was dumb enough to fall for the old 'poisoned cup routine.' As he does so, you can see the supposedly dead Smedly behind him, still breathing normally.
Visible crew/equipment: In the first shot of the theatre play, you can see the boom mike quickly entering the picture to the left on the screen. (00:01:40)
Factual error: During the theatre play you can see they are using electric stage lights. Nice move for a series plotted almost 300 years ago. (00:01:55)
Revealing mistake: The bomb that is thrown at the Prince explodes before the lit fuse actually burns down far enough. (00:03:15)
Factual error: At Ms. Miggins' when she says, "There's ever so much hard work," you can see her wearing a bra under her corset. Bras didn't exist at that time. (00:06:35)
Continuity mistake: When the Shadow shoots at Baldrick to get rid of him, she is aiming over his head but the shot lands at his feet.
Factual error: After the Shadow has left Blackadder a captive, she says how much she hates squirrels, and fires two shots from a single shot pistol.
Continuity mistake: When George (dressed as Blackadder) is in the cellar and about to go upstairs, he has one cup on his tray, however when he arrives upstairs there are two cups on the tray.
Deliberate mistake: There are several historical dates wrong in this episode. For a start, Prince George didn't become Prince Regent until 1811, and yet this is set before the Battle of Trafalgar in 1805 (as Black Adder gives Wellington some advice on it). Similarly, Wellington didn't get the title "Duke of Wellington" until 1814. Again inconsistent with being pre-Trafalgar.
Deliberate mistake: There are a lot of jokes with the name of the book "The Prince and the Pauper." However the book was published in 1881, 51 years after the Prince Regent died.
Factual error: When Blackadder has disguised himself as the Prince and is speaking to Wellington, Wellington says, "I have with me here the most recent briefs from my General in the field". Blackadder, deliberately misunderstanding, replies "If you would like to pop them in the laundry basket". Blackadder is referring to the short, tight style of men's modern underwear, known as briefs, which were not invented until the 1930s.
Deliberate mistake: Whenever a punch is thrown in this series, the punch either stops before it hits the person or goes beside them. It's most obvious in the last episode when General Melchett says 'Excellent native cockney wit' and punches Baldrick.
Continuity mistake: Blackadder chucks up George's helmet, and it gets riddled with bullet holes. When the helmet comes down, it comes down at an angle, revealing that it had been passed down. (00:04:30)
Continuity mistake: When Blackadder, Baldrick and George are out in the no man's land, Blackadder screams and Baldrick asks why. Blackadder answers he put his elbow in a blob of ice cream while looking at Baldrick. When it cuts he is looking straight forward instead. (00:22:20)
Plan B: Corporal Punishment - S4-E2
Continuity mistake: Black Adder shoots the pigeon, and the feathers fly everywhere. One feather lands on Black Adder, just above his ear. In the next shot, the feather has moved up, on the other side of his side-part, towards the top of his head.
Visible crew/equipment: During the general's speech about how Blackadder is the person to organise a concert party, look at the entrance to the trench. In one shot you can see a crew member moving a giant cloth. You see mostly the movement, but you can catch a glimpse of the crew member's face. (00:06:50)
Factual error: Baldrick becomes Blackadder's navigator. The problem is, WWI aircraft did not carry navigators; they carried either only a pilot, or a pilot and an observer, and observers were officers. (00:15:30)
Revealing mistake: When the Baron punches Baldrick into the cell wall, it wobbles. (00:17:20)
Continuity mistake: When Blackadder's plane is shot, we see the bullets hit the side. In the next shot of the plane, not only is the side intact, but fuel is coming out of the bottom.
Other mistake: When we first see the plane that Blackadder and Baldrick are flying, the machine gun on top of it is firing. There are 3 mistakes here. 1) We don't hear the gun fire. Cannot be argued by the plane drowning it out, as we later hear the Red Baron's gun firing. 2) In the next shot, the gun has stopped firing. 3) The fact the gun is firing is ignored by Blackadder and Baldrick. They are too busy on keeping the plane level - the whole flying scene was obviously archive footage of WWI planes flying.
Suggested correction: OK a few points. 1. The baron and Blackadder are flying different kinds of plane. One could be louder than the other. 2. Gunners have to stop occasionally. So the gun stopping isn't a mistake. 3. We don't know for definite if they are ignoring the gun. This is speculation at best.
