Visible crew/equipment: During the Battle of Bull Run, just before the first shell is fired towards the plantation house, at the upper part of the screen you can see a helicopter flying over the battle action. (01:45:00)
Continuity mistake: During the introduction, the snake tries to get away from someone who is supposedly Blackadder. He gets the snake. It's head is above a black tile. There is then a close-up of the snake, Blackadder wags his finger at it. It is now above a white tile.
Continuity mistake: When Buckingham is about to be arrested, the camera is looking directly at him. At this angle, his black fur collar is flipped up, covering the neck of his white shirt. When the scene changes to a wide shot behind him, the collar is folded down. (00:35:00 - 00:35:50)
Replacements - S1-E4
Visible crew/equipment: At the end, as they are moving out there is a high shot of two trucks driving towards the camera. The first truck reflects the camera shadow on the ground. (00:52:20)
Factual error: In the scene, Floki walks towards a small waterfall today known as Kvernufoss. Floki is supposed to be the only inhabitant if not the entire Iceland, at least the region, as we are shown no sign of civilisation whatsoever, and as historical record tell us about Iceland in the early 800s (as the events of Vikings seem to take place). But a well beaten footpath is visible, leading to the waterfall at the end of the canyon. That path is an oft-travelled path tourists follow nowadays to reach Kvernufoss, a well-known site in the area. A path like that in Floki's time would simply not have existed (there is nothing in that canyon but that waterfall, no reason to go there if not for sightseeing) and represents a (tiny) intrusion of our modern world in a show set in the middle age Iceland. (00:37:42)
Continuity mistake: When Prince Charles reads a letter during Camilla's birthday, the paper he holds with both hands is suddenly held with just one. (00:29:07)
Episode #1.1 - S1-E1
Continuity mistake: When the soldiers enter the room after shooting Ae-sin's mother, she is shown lying on the floor. She then turns around and shoots one of soldiers whilst lying on the floor, but when the second soldier shoots her, she is suddenly standing up. (00:58:25)
Continuity mistake: When Rene comes upstairs to speak to Michelle, his hands and arms are covered in cement. However, when he arrives in the cafe from the basement his arms and hands are clean. Not enough time has elapsed for him to clean them all perfectly. (00:03:05)
Factual error: On the map behind the colonel during the first scene, Iceland is labelled as being under Nazi control. This is incorrect, as the British were in control of the country during the whole of the war. (00:05:10)