Steampunk Gadgeteers
Maybe it's because anything before the Renaissance was Medieval Morons, everything invented between World War I and World War II was created by the military and everything from 1950 onward was made by corporations or universities, so they need people to build stuff in a setting with technology but nowhere to buy said technology.
Maybe it's because of the sheer number of inventors in the Industrial Revolution, like Tesla, Charles Babbage and George Stephenson.
Maybe it's due to Rule of Cool.
For whatever reason, there is often at least one Gadgeteer Genius or Mad Scientist in the main cast of any series set in a Steampunk or Gaslamp Fantasy setting. The majority of those don't stop there and make inventors, mad scientists, mechanics, gadgeteers and other masters of Magitek as common as trees in a forest!
Note that this is what this trope is about. If there's only one Gadgeteer Genius or Mad Scientist in a work, it's not this trope. If, however, there is a high ratio of normal people versus tech experts - 3 Muggle characters for every 2 geniuses is probably the minimum - then it falls under this trope. If you've seen any of the series below and they don't fit this criteria, you probably know what needs to be done.
Anime and Manga
- Steamboy [context?]
- Nadia: The Secret of Blue Water: Jean and Hansen.
- Princess Principal: The team goes up against a group of gadgeteers in Case 9.
Live-Action TV
- The Wild Wild West: Artemus Gordon and almost everybody who filled in for him during the second half of the final season.
Tabletop Games
Theatre
Video Games
- Professor Layton and the Curious Village technically counts, since of the five real human beings in the cast, three - Layton, Don Paolo and Bruno - are canonically Gadgeteer Geniuses.
Web Comics
- Girl Genius: Practically all of the Sparks, definitely including Agatha, Gil, and Tarvek.
- The Thrilling Adventures of Lovelace and Babbage: Both of the title characters.