Fake Nationality: Hoo boy. We have Brits playing Italians (Derek Jacobi, Sean Harris, Julian Bleach), Brits playing Spaniards (Jeremy Irons, Holliday Grainger, David Oakes, and Joanne Whalley), a Brit playing a German (Simon McBurney), a Dutch woman playing an Italian (Lotte Verbeek), a Canadian-American playing an Italian (Colm Feore), a Lithuanian playing an Italian (Ruta Gedmintas), a French-Canadian playing an Italian (Emmanuelle Chriqui), and a French-Canadian playing a Spaniard (Francois Arnaud).
Both Jeremy Irons (Rodrigo Borgia) and Colm Feore (Cardinal della Rovere) have played Tom Hiddleston's father at one point or another- Irons as Henry IV to Hiddleston's Prince Hal in the BBC's 2012 adaptation of William Shakespeare's Henriad, and Feore as Laufey to Hiddleston's Loki in 2011's Thor.
What Could Have Been: It was originally supposed to be a film, simply titled "Borgia", with Colin Farrell and Scarlett Johansson as Cesare and Lucrezia, but funding fell through. Director Neil Jordan eventually found the money with the Showtime network, and thus a series was born.