Actor Allusion: Let's be honest, when Claire is chewed out for running through the cemetery, you half expected the old woman to start shouting "BOO! BOO! BOO!" at her.
As Himself: Several prominent American cable news personalities appear as themselves commenting on Underwood's actions including Sean Hannity, Rachel Maddow, and Stephen Colbert (in a final appearance in character)
Directed by Cast Member: In addition to playing Claire, Robin Wright has directed seven episodes of the shownote Chapter 23 in season 2; chapters 35 and 38 in season 3; and chapters 42, 43, 48, and 49 in season 4.
Kevin Spacey has been an executive producer for the show for its entire run. Robin Wright also became an executive producer beginning in season 4.
Name's the Same: Rather bizarrely, Doug Stamper is the only character to have the same last name as their British counterpart (Tim Stamper). Similarly, Francis Underwood is the only character to have the same first name as his British counterpart (Francis Urquhart), and Claire also always addresses him as "Francis"; everyone else addresses him as "Frank" because a Southern gentleman named Francis would insist that you call him 'Frank', and a British aristocrat would faint at the idea.
One of Us: Frank is an avid fan of video games, specifically first person shooters, that he plays at night to help relax. He also has a collection of Gears of War action figures, stolen from Peter Russo's son, that he keeps in his office desk and uses as props to intimidate a pair of junior congressmen to supporting the Watershed bill. The first thing he notices when he visits Peter Russo's condo is his son's PSVita lying on the coffee table. Frank picks it up like a kid on Christmas morning and even asks Peter what games he has for it before finally setting it down.
When Frank Underwood visits Petrov in the Jordan Valley in Chapter 36, the Navy SEAL security team riding in the Hummers with him are all real Navy SEALS that Kevin Spacey worked with on Captain Phillips (on which Spacey served as an executive producer). In particular, the Navy SEAL on his immediate left when Frank steps out of the vehicle is Spacey's actual bodyguard in real life.