Sir Harold was a male anthropomorphic dog who is now a ghost.
A tall bearded man who, judging by his dress and circumstances, was likely a companion of the Mad Duke of Duckburg, Sir Harold lived in a large manor in Duckburg, which he came to haunt after his death. A quiet and unassuming ghost, Sir Harold hates company and ruckus; as a result, while he happily tolerated the Manor's reserved 20th century buyer Scrooge McDuck, he left in a hurry when Scrooge and his nephew Donald attempted to open the "haunted manor" to the public as a tourist attraction.
Behind the scenes
Sir Harold appears in the 1989 story The Shy Ghost.