Detective MacMuffin is the name given PewDiePie to Detective McGuffin in Lucius. He's a detective assigned to different "accidents" at Dante Manor. He gets more and more suspicious as the list of dead grows longer. He is a Catholic; attends confession and offers prayers for the family. He is one of the survivors of the game along with Lucius and Lucifer. PewDiePie expressed a dislike towards MacMuffin's inability to solve the deaths occuring throughout the game, stating that he"sucks at his job," and even a desire to kill him.
In Episode 7 of the playthrough, Pewdie retrieved a gun from a safe, and then went into a room where Charles and MacMuffin were discussing Fabias's disappearance. Pewdie took out the gun and held it right in front of them, only for neither of them to react. Pewdie mocked the game flaw for a moment before shooting MacMuffin, immediately resulting in a game over.
MacMuffin does not actually die canonically.