An easter egg is an intentional hidden message, inside joke, or secret reference to media outside of the game's universe. This is a list of all the Easter eggs that can be seen throughout Watch Dogs 2.
Hidden Cow Level
In the first intro mission, after Marcus gets through parts of CTOS that other hackers couldn't, Sitara calls it the hidden cow level. This is a reference to a hidden level in Diablo 2, dubbed the "cow level".
At the end of the first intro level, Wrench greets Marcus with the Vulcan Salute, a well-known hand sign from the Star Trek franchise.
In the mission Haum Sweet Haum, Marcus breaks into a sample smart house owned by Haum Electronics. The Security Robots that are patrolling the house are named after the ghosts from Pac-Man: Pinky, Blinky, Inky, and Clyde.
Aiden can be seen in a side mission in Watch Dogs 2. He arrives in San Francisco to shut down a human trafficking ring run by the Auntie Shu Gang and Bratva, however he was captured by the Bratva. Marcus Holloway, who was also investigating the trafficking ring, breaks into where they're holding him and hacks Aiden's phone, which was in possession of a guard (along with his Baton). Aiden sees the distracted guard, then glances at the cell camera. He then goes to the guard and defeats him, taking the baton and phone with him before starting a miniature blackout to cover his escape.
Rainbow Six Siege
Far Cry 3: Blood Dragon
In the mission Hello World, Sitara tells Marcus that his mission, should he choose to accept it, is to break into CTOS HQ. The "should you choose to accept it" part is a direct reference to the Mission: Impossible film series, as it is a famous quote that derived from the film series.
Chicago police car
In the mission Cyberdriver, as part of the movie set at HMP Studios, two Chicago Police Department Vessels can be seen, and can even be stolen in the mission. This is most likely not an Easter egg, but more of a mission feature, as the mission features a movie set with the Chicago PD cars being used as film props.
I Know Kung Fu
Right at the beginning of the game, Wrench introduces Marcus to the Research app to upgrade his skills, to which Marcus responds "like I Know Kung Fu!". This is a reference to the 1999 movie The Matrix, where Keanu Reeves uploads a wealth of martial arts knowledge into his brain and says "like I Know Kung Fu!".
Alien and Predator movies
During the last part of the mission Hacker War, Marcus has a full-blown conversation with Wrench about whether Aliens (from the Alien movies) or Predator (obviously from the Predator movies) would win in a fight. Wrench even goes so far as to explicitly name Ridley Scott and James Cameron; Scott the director of the first movie, Alien, and Cameron the director of the sequel, Aliens. They also mention the possibility of Batman and Superman fighting the creatures in their own movie.
Later, in the mission Shanghaied, when Marcus asks Sitara which shipping container to look for, Sitara jokingly answers "LV-426." Marcus then playfully responds "Seriously? You're testing my Geek-Fu?" In the Alien universe, LV-426 is the planet from which the xenomorphs (aliens) originate from.
Towards the end of the mission Haum Sweet Haum, Marcus begins talking to Wrench about swimming with Stingrays, in which Wrench replies "Those fuckers killed the Crocodile Hunter". This is a clear reference to Steve Irwin, an Australian crocodile hunter who was tragically killed by a stingray in 2006.
NPC's can be over heard talking about getting tattoos of the scene where Jack Torrance breaking through a door saying "Here's Johnny!" referencing the scene from The Shining.
Marcus can talk to Wrench, and one of the discussions is about Star Wars characters and places, including Lando Calrissian, Chewbacca, and Cloud City.
Multiple references are made to Ubisoft itself, the company who made Watch Dogs 2:
- The mission Ubi-Stolen starts with an NPC talking about leaks at Ubisoft concerning projects like Unity, Syndicate, and Osiris. These names are references to Assassin's Creed: Unity, Assassin's Creed: Syndicate, and Osiris, a canceled game which is being reworked as the newest installment in the Assassin's Creed franchise. The name of the mission itself is also a direct reference to Ubisoft.
- The exterior of the Ubisoft building features posters for 2016's Assassin's Creed film.
- In the interior, pictures of Assassin's Creed: Unity, Far Cry: Primal, and Rainbow Six Siege, all Ubisoft games, can be seen.
- Some of the employees can be heard talking about Just Dance, another Ubisoft game.
- The pawn shops, like in the first Watch Dogs game, and the San Francisco Hackerspace, have Ubisoft arcade games in them.