Even with The Last Of Us successfully ending its first season, fans of the HBO series are still going over its nine episodes to search for important clues and potential easter eggs that can pop out. And while there are many to discover, so too are its differences from the Naughty Dog it was adapted from. We take a look below at the biggest differences that set the two adaptations apart.

6 biggest differences between The Last of Us HBO series, video game

The Last Of Us, HBO, Entertainment

6. Origin of the outbreak

For years, fans have wondered how the world of The Last Of Us came to be in the video game as there is no clear explanation for the outbreak's start. Even with all the clues and theories floating around, there hasn't been an official confirmation of what happened before the world fell to absolute ruin.

When it comes to The Last Of US HBO series, the prologues of the first and second episodes clear the air on what happened. As it stands, a certain kind of fungi has the ability to take control of its host, as theorized at the start of episode 1. Episode 2, meanwhile, gave viewers a glimpse of how the Cordyceps infection started in Jakarta, Indonesia, and spread all throughout the world from there when it was mixed with flour. Thanks to the Southeast Asian nation being one of the main exporters of flour in the world, it took only a short time before everything went to hell, including what happened to Joel, Tommy, and Sarah.

5. Tess' death

Just as viewers were starting to know Tess more, The Last Of Us season 1 had to kill her off at the end of episode 2. Thanks to a bite she got after encountering several infected individuals residing within the Boston museum, Tess had to sacrifice herself to buy Joel and Ellie time to escape from a horde of undead coming their way. With the pair out of the way, Tess blows herself up to take this group of infected along with her.

In the video game, though, is a different story. After making their way to the Massachusetts State House, they discover that the Firefly group they were supposed to meet has been taken out by FEDRA. With the organization's forces arriving, Tess makes the ultimate sacrifice to give Joel enough time to escape with Ellie. Another notable difference here is that before her death, Tess advises Joel to find Bill for help in the game. In the show, Tess tells Joel to enlist Bill and Frank's help so he can search for Tommy himself instead.

4. Bill and Frank

Bill and Frank's story is perhaps among the biggest changes derived from the source material. In the video game, Bill appears for the first time as a lone individual that will eventually work with Joel and Ellie. He appears to be bitter about Frank, who broke up with him prior to the events to the events of the game. In time, he, Joel, and Ellie will find Frank dead hanging from the ceiling. It's later discovered that he decided to kill himself rather than fully turn into an infected. Plus, he still harbors ill feelings toward Bill, his former lover.

In The Last Of Us season 1, we see that concept turned around and expanded into a full episode. Viewers got the chance to know how Bill transformed his town into a fortress and how he got to meet Frank. Over the years, we see the couple grow in love together amidst various challenges that tested their relationship, as opposed to the antagonistic version we see in the game. In the end, both Bill and Frank chose to end their lives after the latter slowly succumbed to a terminal disease.

3. Kathleen and Perry

After their stop at Bill and Frank's place in The Last Of Us season 1, Joel and Ellie find themselves stranded in Kansas City after a local group wrests control from FEDRA after years of abuse. Kathleen, the local militia leader, is now in control of the said city and is on the hunt for Henry, an individual instrumental in the death of his brother. With Henry and Sam working together with the show's main protagonists, Kathleen tasks her right-hand man, Perry, to take them out by all means necessary.

But just as the four are about to escape the city, Kathleen and Perry's forces corner the group. Before they can apprehend Henry and the others, a huge number of infected attack them, killing Kathleen and Perry in the process. In the video game, though, there is no mention of these two or what they did in Kansas City. As it stands, both Kathleen and Perry are original characters created for season 1 of The Last Of Us on HBO.

2. Ellie and David's first meeting

Back in The Last Of Us season 1 episode 8, we see Ellie encounter David and James out in the open hunting a deer she had been chasing earlier. In her desperation, Ellie blackmails David to give her medicine to help Joel heal from his wound, prompting the older man to order James to get it back from their town. While waiting, Ellie discovers that the men who attacked her and Joel in the previous episode belonged to David's group. Around this time, James arrives with the medicine and Ellie leaves with it right away.

In the game, David and Ellie spent a more challenging time together as a group of infected came out of nowhere while they were waiting for James. This encounter forced the pair to work together, leading Ellie to trust David rather earlier than what was shown in the series. Of course, this is a mistake on her part as it was later revealed that David and his group are cannibals feeding off on their own to survive.

1. The revelation of Ellie's mother and her immunity to Cordyceps

The Last Of Us I and II never delved into Ellie's parents or how she obtained her immunity from Cordyceps. Even though there were a lot of rumors around these two issues, the two video games never really confirmed anything. The HBO series, meanwhile, went above and beyond by showing who Ellie's mother is and how her birth after a nasty bite made the immunity possible. Thanks to Marlene's help, Ellie survived into the present day and made the story of the series possible.

It remains to be seen how these changes will move the story forward in The Last Of Us season 2 or if there it will veer away further from the video game. What's certain, though, is that fans of both the HBO series and the video game must stay tuned when season 2 comes back soon.