Continuity mistake: At the very end of the episode, when it shows you all the dead bodies, you can see Queenie to the right for a few seconds. The dagger she is holding is pointing upwards. Then there is a close-up of Queenie, who then talks back to you in Prince Ludwig's voice, and the dagger she is holding is now pointing downwards.
Continuity mistake: When Blackadder, Queenie and Nursey are all comforting Melchett, there is a shot from the side view of Melchett, he is holding his head with his left hand. Then there is a shot from behind Melchett, he still has his hand on his head but when the shot returns to the side, Melchett no longer has his hand on his head.
Continuity mistake: There is a knock on the front door, and Blackadder tells Baldrick to 'get the door'. Baldrick returns with it, but the front door on the set, still in place, is still visible in the background of the shot. The fact that Baldrick knows who was at the door indicates that he's got the right one.