Captain Gregg is a fictional character from the classic film and play, "The Ghost and Mrs. Muir." He is portrayed as the ghost of a sea captain who haunts a seaside cottage. Captain Gregg is known for his gruff demeanor and strong personality, which often leads to humorous interactions with the living characters, particularly Mrs. Muir. In the story, Captain Gregg forms an unusual friendship with Mrs. Muir, a widowed woman who moves into his cottage. Their relationship evolves as they navigate the challenges of life and love, blending elements of romance and comedy with the supernatural.