1.The receptionist in "USS Callister" is seen using the dating app from "Hang the DJ."
2.The milk Daly drinks in "USS Callister" is made by a company called "Raiman's." Raimin is the name of a character in Season 3's "Men Against Fire," who reveals that she grew up on a farm.
3.Kirsten Dunst has a very brief cameo about 10 minutes into Season 4's "USS Callister."
4.Michaela Coel who starred in "USS Callister" as Shania, also played the airport stewardess in Season 3's "Nosedive."
5.The name of a planet in "USS Callister" is "Skillane IV." Victoria Skillane is the name of the protagonist in Season 2's "White Bear."
6.The voice of "Gamer691" heard at the end of "USS Callister" is Aaron Paul.
7.The violent footage briefly shown to young Sara at Arkangel is from the Season 3 episode "Men Against Fire."
8.In "Crocodile," a "judge of Hot Shots" is mentioned. Hot Shot is the game show from Season 1's "Fifteen Million Merits."
9.A lunchbox can be spotted in Marie's buggy that features Waldo, from Season 2's "The Waldo Moment."
10.In "Arkangel," Sara has a poster of Tusk, the rapper who was targeted in Season 3's "Hated in the Nation."
11.The 18+ video Mia puts on her hotel television in "Crocodile" is by "Wraith Babes," the same adult film company seen in Season 1's "Fifteen Million Merits."
12.Part of the text on the newspaper article Rob shows to Mia pokes fun at viewers who pause to read it.
13.The pizza company called "Fences," is seen in both "USS Callister," and "Crocodile."
14.When Clarke begins to enter the ignition code, text pops up that reads "mianolan," the name of the main character in "Crocodile."
15.After Clarke enters the ignition code, the text references episodes from the first two seasons of Black Mirror. It also says, "why.did.you.bother PAUSING.this.you.freak."
16.The desk Bella rummages through has a "San Junipero" postcard on it.
17.Black Museum is full of references to past episodes, starting with Victoria Skillane, who's photo can be seen on a screen that labels her, a "child killer."
18.The bathtub Mia killed Anan in during "Crocodile" is in there.
19.The tablet Sara beat her mother with in Arkangel is on display.
20.One of the mechanical bees from Season 3's "Hated in the Nation" is shown.
21.The augmented reality technology from "Playtest" can be spotted.
22.Carlton Bloom, who killed himself in Season 1's, "The National Anthem" is visible in the museum.
23.Tommy's lollipop from Season 4's "USS Callister" is also in there.
24.And the outfit worn by the masked man in Season 2's "White Bear" is in the museum.
25.The rats Rolo Haynes talks about experimenting on are named Kenny and Hector, which are also of the names of the two protagonists in Season 3's "Shut Up and Dance."
26.And finally, the graphic novel Jack is seen reading with Carrie titled "15m Merits" depicts a scene from the Season 1 episode, "Fifteen Million Merits."
