Watsonian

Etymology
. "In-universe" sense formed in reference to Dr. John Watson, the fictional author within the text of the stories, in contrast to Sir Arthur Conan Doyle as the real author of the stories. Started in Sherlock Holmes fandom before spreading to other fandoms. Possibly originating in the "Baker Street Irregulars" fan club and entering the science fiction fandom usage (fanspeak) via the Lois McMaster Bujold mailing list.

Adjective

 * 1) Resembling or characteristic of the character  from the Sherlock Holmes stories.
 * 2)  From an in-universe perspective; of or relating to an explanation within the text; internal to the narrative.