Working through season 7 for the first time.

In S7E9, they introduce the Ghost of Brooklyn, a serial killer whose DNA was found many seemingly random places. I didn't realize until the reveal that it was directly inspired by the Phantom of Heilbronn, which I coincidentally read about yesterday!

https://en.wikipedia.org/wiki/Phantom_of_Heilbronn

Both Elementary's Ghost of Brooklyn and the real-life Phantom of Heilbronn were actually employees at the factory that made the cotton swabs used to collect DNA samples, hence why their DNA was at many different crime scenes.

Sherlock tells Joan "the thing that's different about me, empirically speaking, is you." I love them so much. 🥹