One of the classic Holmes characters from the canon who shows up in a variety of forms in Sherlock Holmes adaptations is Inspector Lestrade. Conan Doyle never gives us his first name, only his first initial: G. Thus, in Sherlock, he has become Greg Lestrade, a considerably more attractive and intelligent character than he seems to be in the stories; in Elementary, he's Gareth Lestrade, a rather typical Scotland Yard detective, who knew Holmes from his old life in London. And of course he's shown up in various other adaptations, usually as a somewhat unpleasant, sniveling sort of officious detective who has little respect for Holmes's abilities, yet always depending on him for help.
Lestrade is a character who appears in the canon far more than Irene Adler, Mycroft Holmes, or Professor Moriarty, and yet he seems less necessary to the Holmes mythology than those character. Perhaps that mysterious first name is part of the elusive nature of the character? Certainly, Series 3 of Sherlock played around with that first name quite a bit, by milking a shtick where Sherlock continually misremembers Greg Lestrade's name, referring to him by a variety of G names. Elementary, of course, chose to go with another of the interchangeable Scotland Yard detectives, Tobias Gregson, choosing to rename him Thomas Gregson.
Then, of course, there is the everlasting debate about how to pronounce Mr. Lestrade's name. Is it Le-STRAYD or Le-STRAHD? I have usually heard the latter, but one will occasionally hear the former. And knowing how the British are about pronouncing foreign names, the Le-STRAYD pronunciation wouldn't surprise me.
Overall, in Lestrade we have somewhat a non-entity, a character who seems to exist solely for the purpose of highlighting how intelligent and resourceful Sherlock Holmes is as a detective. Lestrade (and Gregson and Athelney Jones) represent the status quo for Scotland Yard: glory-seeking, non-imaginative, and completely dismissive of Holmes's methods. Lestrade isn't completely unlike Watson, but whereas Watson embraces the amazing deductive powers of Holmes that always leave him dumbfounded, Lestrade seems to be completely unaware of how brilliant Holmes really is. A non-entity, yes, but one who makes Holmes's brilliance shine all the brighter.
I'm a stay-at-home dad, and Director of Music Ministries at a United Methodist Church in Mt. Juliet, TN. And a longtime fan of Sherlock Holmes.