Character mistake: After firing Percy and Baldrick, Edmund says to Baldrick that he'll probably go back to shovelling dung in the gutter where Edmund found him. In the pilot episode The Foretelling, Edmund actually met Baldrick when Baldrick was pouring a drink for Edmund.
Continuity mistake: In Back and Forth, the 'modern' Edmund makes off with the helmet we saw Georgius put on the wall. But in the next shot of the Roman Blackadder and Georgius, the helmet is still where Georgius left it.
[Blackadder puts the phone down.]
Baldrick: Who was that?
Blackadder: Strangely enough Baldrick, that was his Holiness Pope Gregory IX, inviting me to join him for drinks aboard his steam yacht, the Saucy Sue, currently wintering in Montego Bay, with the England cricket team, and the Balinese Goddes of Plenty.
Baldrick: Really?
Blackadder: No, not really. I've been ordered to HQ - no doubt means that idiot General Melchett is about to offer me an attractive new opportunity to have my brains blown out for Britain.
The Witchsmeller Pursuivant - S1-E5
Trivia: There are in fact two versions of the bonfire scene. Although most countries use the intended censored version (where somebody coughs right as Edmund says the F word) there are a few US editions where you can hear him swearing uninterrupted.
Question: Who played the balladeer and why was Blackadder trying to kill him?
Answer: Tony Aitken played the Balladeer. Blackadder wants to kill him because he annoys him and usually sings songs about what a fool he is.