|First appearance||"Duel and Duality"|
|Last appearance||"Duel and Duality"|
|Episode count||1 Episode|
|Played by||Rowan Atkinson|
MacAdder (played by Rowan Atkinson) is the nearly identical — though red-haired — Scottish cousin of Mr. E. Blackadder. He is known as being the "most dangerous man ever to wear a skirt in Europe". He believes he is rightful king of England and plans to incite rebellion, meaning his cousin hates him. He is apparently a skilled swordsman, but also a kipper salesman and married to a woman named Morag back in Scotland though he initiates in an affair with Mrs. Miggins. He had two children, a boy named Jamie and girl Angus. Edmund Blackadder wants him to take his place in the duel with the Iron Duke of Wellington to which MacAdder replies: "Why don't I take the place of the Duke of Wellington and kill the Prince?" Edmund Blackadder tells MacAdder that if he does this he will incur the wrath of the bailiffs. MacAdder thereby declines and leaves for Scotland with Miggins, foiling Blackadder's plan.
It's possible that McAdder is related to Blackadder due to how the first Blackadder, Prince Edmund, was supposedly born of an extramarital affair between Queen Gertrude of Flanders and Donald MacAngus, 3rd Duke of Argyle, though this was never fully confirmed or disputed on screen, so it may just be a coincidence.