Sherlock Holmes:

Sherlock is the protagonist in the series, he’s also one of the main characters.
Sherlock has an extraordinary brain, he sees things most people would never even notice. He has also a kind of photographic memory, he stores all his information in, what he calls, his ‘mind palace’.

Sherlock is the world’s only consulting detective; he helps Scotland Yard with solving crimes (especially murders). He describes himself as a high-functioning sociopath. He can be very rude and has poor people skills, he cares more about the crime than about the victim.

Sherlock is a round and dynamic character, Sherlock has a lot of background story and at the end of the series you know almost everything there is to know about him. His character changes throughout the series, in the first episode it’s mentioned that Sherlock Holmes doesn’t make friends, and at the end of the episode he has John Watson who becomes his best friend.

Mrs. Hudson:

Mrs. Hudson is Sherlock’s and Watson’s landlady, she is minor character.
Mrs. Hudson is one of the few people Sherlock trusts. She gets very annoyed when she discovers human body parts in Sherlock’s kitchen.
Upon first meeting John she thought he and Sherlock were in a relationship.

She is a flat and static character, she doesn’t have much of a background story and her behaviour stays the same throughout the series.

Greg Lestrade:

Greg Lestrade is a minor character, and you don’t know much about him, what makes him also a