The Easter Eggs You Missed In ‘Black Mirror’ Season 4 Tie The Show’s Universe Together

Each episode of Black Mirror introduces audiences to a brand new world with surprising new characters and terrifying new tech. While every installment seems to take place in a universe all its own, as the series has gone on, certain stories have begun connecting across episodes and referencing each other. There are no shortage of Easter eggs in Black Mirror Season 4, especially in its season finale, and they help pull the entire Black Mirror universe together. Whether tech from other episodes is popping up, iconic music cues are returning to the series, or actors are being seen again in bigger roles, there are plenty of references to dig through.

In a Reddit AMA, show creator Charlie Brooker revealed that the episodes "take place in the same psychological universe, certainly," further explaining that there are "sometimes explicit links" between episodes. While some episodes may share a fictional TV show, other episodes feature direct references to other episodes, whether that's technology or characters from Black Mirror past.

Even the most attentive viewers may miss these Easter Eggs the first time around, but there are shocking twists hidden in each of these episodes. So there's no television series that yearns for a second viewing quite like Black Mirror. Here's what you ought to be looking out for on that repeat marathon. Oh — and there will be SPOILERS for each of these episodes.

"USS Callister"

Black Mirror's season-opener appears to be a Star Trek pastiche, but like everything else in the show there is a dark, twisted underbelly to the shiny, colorful surface. It also features some subtle references to Season 3, including:

• "USS Callister" features the role of Black Mirror alum Michaela Coel, known as the star of Netflix show Chewing Gum. Coel was last seen in Season 3 episode "Nosedive," playing a particularly difficult airline employee.
• Robert Daly is seen drinking from a carton of Raiman's Milk. Raiman's is not a real milk brand — but Raiman is the name of one of the main characters in Season 3's "Men Against Fire."
• When talking to his newest employee about his favorite television series, Space Fleet, Daly explains that even though he has the entire DVD collection, that "Netflix has it these days," in a nod to its own streaming platform.

"Arkangel"

This Jodie Foster-directed episode finds the horror in app-enabled helicopter parenting, and gains a lot of traction by reusing previously seen tech.

• When showing off the Arkangel's censorship abilities, a violent clip from the Season 3 episode "Men Against Fire" is used as a demo. Arkangel's alternate reality projections aren't all that different from the military-grade technology used in "Men Against Fire" to make human beings look like grotesque monsters.
• The Arkangel technology features a "memory wheel" that could have been modeled after the similar memory archive design seen in Season 1 episodes "The Entire History Of You."

"Crocodile"

The episode "Crocodile" features a number of references to one of Black Mirror's very first episodes - Season 1's "Fifteen Million Merits"

• While scanning the hotel On-Demand Video for pornography, a title called "Best Of Wraith Babes" is shows. Wraith Babes is the pornographic show featured in "Fifteen Million Merits" that the character Abi ends up on.
• The song "Anyone Who Knows What Love Is (Will Understand)" by Irma Thomas is featured heavily throughout the episodes, having been playing from a car during the pizza truck accident. The song was first introduced into the Black Mirror universe when Abi performed it on fictional reality show Hot Shot in "Fifteen Million Merits." The song has reappeared multiple times, including as a karaoke track in "White Christmas," and is sung by the character Raiman in "Men Against Fire."

"Hang The DJ"

"Hang The DJ" is Black Mirror's version of a romantic-comedy. It's got one of the most uplifting endings since Season 3's "San Junipero," but doesn't feature many references to past episodes. However, attentive viewers may recognize the dating app seen at the end of "Hang The DJ." The receptionist at Callister is seen swiping the very same dating app at the beginning of "USS Callister."

"Metalhead"

"Metalhead" is Black Mirror's most sparse episode yet, having been filmed entirely in black and white, and featuring almost no dialogue. However, the dialogue that is featured in the episode harkens back to the show's very first episode. "Metalhead" begins with an extended conversation about the pigs that no longer occupy farms. The Prime Minister in "The National Anthem" surely dreams of a world without pigs based on his history with the farmyard animal.

"Black Museum"

Black Mirror saved its most fan-service friendly episode for the very end of Season 4. Rolo Haynes’ Black Museum is a smorgasbord of Black Mirror history. Rolo promises a collection of authentic criminological artifacts, and delivers by showcasing some of Black Mirror’s most criminal-laden tech.

Featured among Rolo’s many artifacts are:

• A robotic bee from “Hated In The Nation.”
• The cracked Arkangel screen from “Arkangel.”
• The hunter’s outfit from “White Bear” – as well as a miniature exhibit on the details of the case.
• The DNA-scanning machine from “USS Callister”
• The blood-stained bathtub from "Crocodile"

In addition to the physical exhibits, "Black Museum" also features spoken references to "San Junipero," ("Like when they upload old people to the cloud.") and "15 Million Merits" is featured in the form of a graphic novel read by a character in one of Rolo's stories.

Of course, Rolo Haynes' museum is burned to the ground at the end of the episode, and all of the technology inside with it. It hasn't yet been confirmed if Black Mirror will return for a fifth season – but there's always a chance that one of the pieces of Rolo's "Black Museum" is simply the focus of a story that hasn't been told yet. Only on Black Mirror could fans possibly find Easter eggs for episodes that don't even exist yet.