In "Mr. Stink" by David Walliams, Mr. Stink is a central character who is described as a scruffy, smelly man living in a park. He has unkempt hair, worn-out clothes, and a general appearance of neglect. Despite his unpleasant odor, he has a kind heart and a gentle nature. He befriends a young girl named Chloe, who sees beyond his exterior and understands his struggles. Mr. Stink is also known for his whimsical personality and love for storytelling, making him a memorable and endearing character in the story.