Another year means yet another Call of Duty entry, and this year's offering is Black Ops Cold War a direct sequel to 2010's Call of Duty: Black Ops. With so many returning characters and taking place several years afterwards, one expects many nods and references to the first game.

Related: 5 Ways Black Ops: Cold War's Campaign Is Better Than Modern Warfare's (And 5 Ways It's Worse)

The campaign includes numerous Easter eggs and homages for avid fans who have been keeping up with the series' single-player modes all these years. Gamers won't be lost if they do not understand these shout-outs, but fans will feel like their following the first-person shooter franchise has paid off in a few big ways.

10 Friedrich Steiner

Friedrich Steiner

Despite being dead for many years, the name Friedrich Steiner comes up during the course of the campaign. Fans remember him as the Nazi scientist who developed the Nova 6 gas which fuels the first Black Ops' narrative. He also tries to brainwash Alex Mason after the protagonist falls into enemy hands. The mind control did not take like Steiner planned, but the experiment did a real number on Mason's mind.

9 The Numbers

mason aiming gun at jfk in black ops 1

The debut Black Ops title focuses on the mystery surrounding a series of numbers. Occasionally they would pop up on screen, deepening the mystery.

Related: 10 Pro Tips For Call Of Duty: Cold War You Need To Know

The mission "Echoes Of A Cold War," where players controls Alex Mason, features two moments where the numbers pop up, showing he is not completely free from his time in enemy hands. The game still never resolves whether he actually killed President Kennedy or not after heavily implying he did.

8 Dragovich

Dragovich from call of duty

Nikita Dragovich receives lip service during the campaign. To anyone who is playing the series for the first time, this may seem like a throwaway line referencing some mission the characters did outside of the games. However, fans know Nikita Dragovich as the main antagonist of the first Call of Duty: Black Ops. He is also responsible for brainwashing Alex Mason and for manufacturing the Nova 6 nerve agent.

7 Brainwashing

negative objective reactions

With the Black Ops name comes certain expectations from the story. Instead of a straightforward military shooter, there is bound to be some form of mind control or brainwashing. Even Black Ops III, which has few connections to the other games in the series, dives into third act madness, making the player question everything about the story. Black Ops Cold War similarly includes a brain trip as a part of the narrative. Without spoiling too much, just know that not all is as it seems, but fans already knew that before even buying the game.

6 Woods

woods in front of fire

Several characters from prior Black Ops games return in the campaign. Frank Woods is a fan favorite, and players were glad to see him alive in Black Ops II after he was thought dead in the first game during the Vietnam missions. He spent years as a POW, but made it out alive eventually and plays a pivotal role in Black Ops Cold War. Unfortunately, it is a different voice actor, and his personality is a little different. He feels more like comedic relief this time around.

5 Imran Zakhaev

Zakhaev black ops cold war and gorbachef

One mission sees the player infiltrate the Lubyanka Building, or the KGB headquarters. While playing as the double agent inside the building, players attend a meeting where a young Imran Zakhaev is present. Fans of the Modern Warfare games will remember him as the villain of the 2007 title. He is so young here, and has two arms, a problem Captain Price fixes in the classic "All Ghillied Up" mission from Call of Duty: Modern Warfare.

4 Kravchenko

Black ops cold war kravchnko

Also in the meeting during the mission is Mikhail Gorbachev and, more relevant to this article, Lev Kravchenko. This monster of a human was an antagonist in the first two games, starting as Dragovich's right hand man and then playing another villain role in Black Ops II. True to the character's personality, Kravchenko is bestial and described as enjoying interrogations a little too much.

3 Sleeper Agents

Parker Black OPs Cold War

Along with the references to Nikita Dragovich comes with the idea of sleeper agents within the United States, one of the villain's many schemes to try and bring down the west.

Related: 10 Espionage Thrillers To Play If You Liked Call Of Duty: Black Ops Cold War

This was a major plot point of Black Ops from 2010, and receives mention in the new game during cutscenes and at a computer terminal. Alex Mason himself was a sleeper agent, though no one knows how successful this project was.

2 Alex Mason

alex mason sitting alone black ops cold war

Alex Mason is only a minor character in Black Ops Cold War, though he is one of the few playable characters other than Bell. His lack of personality or impact on the plot comes as a surprise to fans, because he is the main character from the first Black Ops. He was never the most beloved protagonist of the franchise, especially when compared to people like Soap and Captain Price.

1 Different Voice Actors

call of duty 2020

To many, whoever voices the characters may be irrelevant. However, fans will immediately notice something off about their favorite characters when the voice actor is changed. Many were disappointed to see the original actor for Woods left out of the picture. Additionally, Hudson has always had a different voice in each game, and this is the first time a notable celebrity did not take on the role in a mainline Black Ops game. Alex Mason was voiced by Sam Worthington in the first Black Ops, but he left the role afterwards.

Next: 10 Biggest Fixes Call Of Duty: Cold War Needs