Episode #1.6 - S1-E6
Trivia: In the park where PS Budd is surrounded by armed tactical response officers, a careful observer would notice that the brand of ear protection devices the officers are wearing are Z-TAC, an airsoft brand.
The Guardian - S1-E5
Trivia: Stan Lee makes a cameo describing the Division's operative as being like a superhero. (00:07:00)
If This Be... M.O.D.O.K.! - S1-E1
Trivia: When M.O.D.O.K. and Austin are out on town, the places they visit make references to several other Marvel characters. The dragon that is serving them in the restaurant is Fin Fang Foom. The concert they are next shown to be attending is advertising Lila Cheney, who in the comics is a mutant who can teleport over interstellar distances. Lastly, the arcade belongs to Arcade, who is primarily an enemy of the X-Men. (00:10:27 - 00:10:58)
Trivia: Intended to be a homage to the cult TV shows "The Fugitive" and "The Prisoner."
Trivia: Shooting scenes with Salem proved pretty difficult for Kiernan Shipka, who discovered on set that she's actually allergic to cats.
Trivia: As Frank is running up the stairs in the FBI, just before he meets Peter you can see "Mulder and Scully" walking down the stair case - this is in fact David Duchovny and Gillian Anderson's stand-ins, but they do look a lot like them.
Alienation - S2-E2
Trivia: Pierce and Moretti are questioning a woman at her front door. The doorbell chime is the theme from Close Encounters of the Third Kind. Fittingly, she thinks her husband was abducted by aliens.
Trivia: Spooks does not have actor credits at the end. The Internet Movie Data Base even lists the lead actors as 'uncredited' for many seasons.
Trivia: Lara Parker, who plays Madelaine the witch in this episode, also played Angelique, the witch in the TV series, "Dark Shadows."