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.
Revealing mistake: When Percy is holding the 'Green' in his hands, light of the green reflects on the wall behind Blackadder. However the way Percy is holding the 'green' in front of Blackadder, Blackadder's shadow should be on the wall behind him, but it isn't. It's obvious green lighting is used to light up the back wall. (00:18:20)