* ActorAllusion: This isn't the first time Robson Green (Colonel Locke) plays a soldier; his StarMakingRole was as Fusilier Dave Tucker on Soldier Soldier.
** Will Yun Lee has formerly played an antagonist North Korean back in Die Another Day.
* FakeNationality: Both the Cinemax leads. Specifically:
** FakeBrit: Stonebridge, played by Philip Winchester (American).
** FakeAmerican: Scott, played by Sullivan Stapleton (Australian).
** Karl Matlock is also a FakeAmerican, played by Irish actor Vincent Regan.
** Pakistani terrorist Latif is played by British actor Jimi Mistry, whose parents are Irish and ''[[{{Irony}} Indian]]''.
* HeyItsThatGuy:
** Given the obscurity of Series/ChrisRyansStrikeBack outside of Britian, Creator/RichardArmitage's appearance as Porter may count as this to American audiences.
** Hugh Collinson eventually became [[Series/TheWalkingDead a sheriff fighting to survive a zombie apocalypse]].
** [[Series/{{Arrow}} Walter Steele]] is a liaison between Section 20 and the government.
** [[{{Series/Lost}} Mr. Eko]] held [[Series/GameOfThrones Ser Jorah Mormont's]] daughter ransom for guns in ''Project Dawn'', episodes five and six.
** [[Series/GameOfThrones Tywin Lannister]] is ''Vengeance'''s BigBad, and is up to his usual trick of manipulating the geopolitical climate for his own benefit.
** [[{{Film/Underworld}} Sonja]] was in charge of Section 20 during ''Vengeance'' and the beginning of ''Shadow Warfare''.
** Series/DocMartin appears as a retired MI-6 officer living in Beirut.
** [[WireInTheBlood Dr. Tony Hill]] is Section 20's new boss, replacing Dalton.
* OldShame: Sullivan Stapleton grew embarrassed of his character's frequent sex scenes because they didn't do much to advance the plot and because he'd have to simulate sex with actresses he'd meet just before shooting said scenes. He eventually asked the writers to at least give some sort of explanation as to why Scott was so promiscuous, leading to the revelation, developed through the later portions of Series 3 and throughout Series 4, that Scott had been so traumatized by his experiences that he is desperately searching for intimacy.
* PlayingAgainstType: Michelle Yeoh as Mei Foster. You'll find out.