Visible crew/equipment: When Blackadder is called to the Queen's first practical joke and he says he didn't laugh because his head would fall off, the Queen says, "If you don't start soon, your head will fall off", the boom mike is visible above her head. (00:09:55)
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)
Answer: The closest we ever get to knowing his first name is in series 3, when he claims it's "Sod Off". Blackadder asks him in series 3 where this came from, and he replies "Well, when I was a kid, living in the gutter, I'd go up to the other kids and say 'Hello, I'm Baldrick'. And they'd say, 'Yes, we know. Sod off, Baldrick.'" The S in this series is likely a reference to that, but it's not addressed, and given this Baldrick is clearly different from the series 3 Baldrick, we can't draw a direct link.
Shay