- ❝ In football, trying to run out the clock and hoping for the best never works. It’s called “prevent defense.” You don’t take any chances and just try and hold on to your lead. But prevent defense just prevents you from winning! It’s always better to try something. ❞
- —Jason to Eleanor, Michael, Janet and Tahani.[src]
- ❝ Jason: "Michael said that there is nothing he could say that would make you realize he's really him. But Janet does have a thing she can say that does make me realize she is really not her!"
Jason: "I called Janet 'girl' but she did not say 'not a girl.' The real Janet always says 'not a girl'." ❞
- —Jason learns Janet is not Janet before anyone else.
In life, Jason was often considered dumb, and was a misguided man who had major impulse issues. While not a violent person, he believed every problem could be solved by throwing a Molotov because throwing the molotov replace any previous problems with a new problem. Rather than getting an actual job, he preferred relying on his amateur DJ'ing skills and would resort to robbery, theft, and even scams if it meant making quick money.
Due to drug use, a poor education, and possibly a legitimate neurological condition, he has a low IQ, described by Michael as that of a seven-year-old (Chapter 11: What’s My Motivation). In Chapter 51: Patty Jason says that a doctor once said that his brain was "smooth as an egg". Taken at face value, this means Jason suffers from Lissencephaly, a neurological condition that causes, among other problems, low intelligence and impulse control problems. If this is true, Jason was never dumb or bad, but mentally handicapped. Whatever the cause, his symptoms include an inability to make logical connections, lack of object permanence, frequent malapropism (such as saying "learn about Ethnics" instead of saying "learn about ethics" or "bleach of contract" instead of "breach of contract"), and low speech fluency.
Once he died and arrived in Michael's neighborhood, he was forced to take on the role of Jianyu, a silent monk. Knowing that he didn't belong, he decided to go with the lie and reveals he was initially scared the first couple of days. When Eleanor and Chidi get through to him that he is not supposed to be there like Eleanor, he is able to force himself to go to Chidi's Ethic's Class.
As Chidi's lessons continue, Jason slowly begins to gain control over his impulses, albeit barely. By the time of Season 3, he has gained tremendous control over his impulses that he earned praise from Judge Gen, though still failed his impulse test.
Tahani points out that he has massive amounts of unearned confidence, which in turn also makes him good at sex.
Jason also appears to have a harder time connecting with people emotionally, seen when he didn't feel anything if Tahani and Chidi got sent to The Bad Place instead of Eleanor and himself. But when faced with the real possibility of going to The Bad Place, he apologizes to Tahani for lying to her and for everything else he did, showing that he does know empathy.
While he has a hard time connecting emotionally, Jason is capable of unconditional love. With Janet being the only person who is ever really nice to him, he falls in love with her and is willing to fight for her when threatened, like at the barfight in Canada; he is even willing to going as far as to break into The Bad Place to rescue her, despite the risks.
Despite his low intelligence, he has had moments of insight. He was the first to guess that the Good Place in Season 1 wasn't what it seemed, guessing that he is "on a prank show" (Chapter 4: Jason Mendoza). He's the only person, besides Eleanor, to figure out they're in the Bad Place, which significantly distresses Michael, causing him to say "Yeah, this one hurts" (Chapter 16: Dance Dance Resolution). He was the one to figure out that Janet was being impersonated by Bad Janet (Chapter 43: Tinker, Tailor, Demon, Spy). Chapter 22: Leap to Faith reveals that Jason is the only person who has noticed The Panda (A teleporting Panda is concealed in the background multiple times throughout the series. No one ever seems to notice it. The reason behind this is never addressed.) In Chapter 13: Michael’s Gambit Jason accurately defends his position using the philosophy of Consequentialism (pronounced correctly).
Jason Mendoza was born in a swimming pool after his mother jumped in doing a "cannonball". His father is Doug Mendoza, whom everyone calls Donkey Doug, even Jason. His mother died from cancer when he was young, her name is never mentioned but it is suggested that she had a careless and impulsive personality like that of Jason and Donkey Doug. Much of his early life is unknown, other than that he liked to do whip-its while in school and he met his best friend Pillboi. While his father began going to school to be an electrician, he never finished and became a stoner, having his own son referring to him as Donkey Doug.
When Donkey Doug was going to move away and leave his dance crew, Jason and the rest of the dance crew framed the woman he was going to leave with for a crime so that he had to stay since Doug was their "best pop-and-locker".
At some point, he participated in a Jalapeno Poppers Eating Contest at a restaurant called Stupid Nick's, winning by consuming over 50 jalapeño poppers in less than a minute, surprising the hospital staff. Stupid Nick's became his favorite restaurant afterwards.
Jason became an amateur DJ, though refers to himself as "pre-successful" and went by the name Mr. Music The DJ. He sent his recordings around to other artists and received no word from them. One by the name of Acid Cat harshly tells Jason he has no talent, but that he can impersonate him at a night event while the real Acid Cat performs elsewhere. Jason is excited at first, but after a week begins feeling depressed as the crowd isn't really cheering for him. He then decides to reveal that he is not actually Acid Cat and plays his own track. He is quickly boo'd off the stage and is sued by Acid Cat for breach of contract. In an act of revenge, he and Pillboi toss a Molotov at one of Acid Cat's boats and run.
While in a diner, Jason and Pillboi discuss how they need to come up with funds to "live the life they deserve" and Jason as the idea of robbing the Mexican food restaurant they are eating at. His plan is to hide in a safe, doing a bunch of whip-its in the process, while Pillboi installs the safe; Jason would then come out and steal the money and Pillboi would return to get the safe. However, Jason fails to realize that a snorkel would not help him breathe when there are no air holes in an air-tight safe and suffocates rather quickly.
Jason Mendoza was mistaken for Jianyu Li, a Taiwanese monk. When he arrived in the Good Place, he was asked by Michael if he would like to continue the vow of silence he took while he was alive.
He nodded that he would like to, confused at what was going on. But this proved to be a problem with Tahani Al-Jamil as his soulmate, as she kept pressuring him to speak. Jason sat behind Eleanor during the orientation video that Michael showed to the residents.
Later that day, Tahani threw a party at their house. There, Eleanor (while drunk) told him that she didn't belong in the Good Place. The next day, Jason slipped a note under the door of her house that said "you don't belong here."
The day after that, he sent her another note that instructed her to meet him that night. Eleanor meets Jason and he explains his actual identity. Eleanor starts helping Jason connect with Tahani without revealing his true identity and Jason begins taking ethics lessons as well.
To avoid Jason revealing his identity to Tahani, Chidi tags along on a couple's spa retreat and helps Jason connect with and cheer up Tahani. When Michael announces his retirement, Jason helps Tahani throw Michael a party and later inadvertently causes Chidi to reboot Janet, as Jason followed Chidi and Eleanor to the beach. After Eleanor gives herself up Jason avoids detection by continuing his silence. Once they think Eleanor is leaving, Jason goes with Tahani to Eleanor and Chidi's house to say goodbye to her.
During Michael's negotiations with the Bad Place group, Jason is around and helps out with random things, which leads Tahani to realize that he's not Jianyu. Jason finally starts talking about who he is and Tahani's disappointed. Jason's sad and afraid he'll go to the Bad Place, so he asks Janet to cheer him up and she brings him food he likes, causing Jason to feel that he loves Janet and ask her to marry him. Janet brings Eleanor and Tahani invites to the 'wedding' and they witness Jason's EDM wedding march-scored, nude pic/bortles shoutout-vowed ceremony.
Jason, thinking Michael is Janet's Dad, confesses his real identity to Michael. Michael tries to deduce his character by giving him the same test Eleanor got, with all of Jason's answers proving him a Bad Place candidate. After Michael reminds Jason how he died, Jason calls Janet and tells him they can't be together because he's dumb. When Michael wants to reboot Janet, she brings Jason (and Eleanor) to The Medium Place to escape being separated. While there, Janet and Jason spend their time trying to figure out how to have sex.
After they get the message through Janet that Chidi and Tahani will be sent to the Bad Place in their stead, Eleanor tries to convince Jason that they should save their friends, as Janet will only bring the train back to the neighborhood if Jason agrees. After Eleanor explains how rotten her parents were to her and how this is a chance to do something right for both her and Jason, he relents and they return to save Chidi and Tahani. Shortly after, Shawn gives them half an hour to decide which two of the four of them will go to the Bad Place and Eleanor realizes they are in the Bad Place.
In Attempt #2, Jason is paired with Luang, another monk having taken a vow of silence, as his platonic soulmate.
Jason is soon unhappy with the arrangement and ends up connecting with a newly rebooted Janet, having an exchange similar to their first one where Janet helps Jason and he hugs her, prompting her to ask him why he hugged her. Eleanor's note helps her figure out they're in the Bad Place in two days and Jason reveals his true identity just before Eleanor's second epiphany.
The following attempts always end up with Eleanor's epiphanies, except one time where Jason, to the astounded horror of Michael, is actually the one to figure it out. At Attempt #802, Michael actually asks Jason for advice and casually mentions that they're in the Bad Place.
Simultaneously, Chidi and Eleanor overhear some of the demons talking about how they're in the Bad Place, tell Tahani and try to formulate a tactic to somehow fight Michael. Eleanor taunts him with the fact that she always finds out and Michael tells the humans he wants to team up with them.
After Michael saving Jason from suffocation in the safe, he tries to change, focusing more on his dance troupe, and forbidding them from committing crimes. After losing a dance competition, Jason lifts the ban on crime from his group, and chaos ensues. Jason decides to go to Sydney, Australia, because Michael convinced him, under the alias of “Zack Pizzazz.” Jason goes to Australia, and joins an experiment Chidi started for people who had near death experiences.
Michael and Janet return to Earth, due to Bad Place demon Trevor infiltrating the group of the four humans. The humans soon find out that they were once in the afterlife, and of course Jason had no idea what was happening.
The humans’ bodies all dematerialized on Earth due to Janet taking them into her void to narrowly escape several Bad Place Demons in a bar near Calgary. They all looked like Janet after arriving in her void, and because of his behavior, Jason was easily distinguishable. Jason and Tahani find out that he and Janet were married in one of the reboots, causing all three of them to be confused about their feelings for each other.
The humans travel to the Neutral Zone, a zone that is neither The Good Place or The Bad Place. They meet Judge Gen in the inter-dimensional hole of pancakes, “The IHOP,” and she reprimands Michael for screwing up the experiment of sending the humans back to Earth.
At the end of Season 3, Jason and the rest of the humans travel to The Medium Place for a new four-human experiment. Jason is really no help.
In the final episode, Jason spends time with his father, Donkey Doug, and he accomplishes one of his final life goals after over 400,000 tries: playing the perfect game of Madden. He begins to feel complete, but tries to brush off his feelings. He tries and fails to make a dinner for two for him and Janet, but both of them realize that his Afterlife is complete and it's time to walk through the Last Door.
After breaking the news to his close friends, Jason, Chidi, Eleanor, Tahani, Janet, and Michael, they all throw him a going-away, party with many people Jason knew in life, like Donkey Doug, Pillboi, and his 60-person dance group in attendance. During the party, Jason confides in Eleanor and Chidi and tells them that he's worried that Janet might forget about him, and shows them a necklace, carved with the initials "J&J" in it, that he made for her. Eleanor reassures Jason that Janet could never forget him because its literally impossible for her to forget anything, and that Jason is not the kind of person easily forgotten.
The next day, Janet leads Jason to the Last Door where she instructs him what to do and they have their final goodbye. Jason realizes that he lost the necklace he made for Janet and worries. Janet comforts him, explaining how time works differently for her, and that she lives in all times at once, so to her, Jason will always be there. The two share a kiss, and Janet tells Jason to enter the Last Door whenever he's ready, and leaves him.
Over 1000 Bearimys later, Janet returns to the Last Door, and instructs Chidi on what to do when entering the door. As Chidi enters the Last Door, Jason appears behind a tree saying that he found the necklace he made for Janet, and simply waited until she returned to give it to her. Jason described how his time alone let him reflect, think, and meditate. Janet compares his time alone to the life of a monk, which confuses Jason. He gives the necklace to Janet, gives her a final kiss and says his final goodbye, and runs to the gate yelling "Chidi, wait up!" before running through the door and ending his existence in the universe.
- ❝ Yo, you should listen to me, I came up with hundreds of plans in my life and only one of them got me killed ❞
- —Jason to Eleanor
- ❝ I wasn't a failed DJ, I was pre-successful ❞
- —Jason to Michael[src]
- In Mandarin Chinese, "Jianyu Li" (监狱里) means "in prison" or "in jail", comparing his time under the guise as a prison to him, as he wasn't able to speak or act like himself.
- Jason is Filipino, and thought that Michael and everyone else in the fake Good Place was racist for thinking he was Taiwanese.
- Jason's DJ name was Mr. Music the DJ.
- Jason is a big fan of the Jacksonville Jaguars American football team. He yells "Bortles!" (as in Blake Bortles, the team's star quarterback) before throwing Molotov cocktails.
- Jason loves Ariana Grande.
- In Season 2, Jason mentions how Tahani taught him to not to eat candles because they smelled good.
- Jason thinks penguins are mythical animals.
- Jason is the only member of the main cast to have been in multiple romantic relationships with other members of the main cast, having married Janet in the first version of Michael's experiment, sleeping with Tahani in another version and even marrying her after they are all resurrected (though they only married on Earth so Tahani could transfer 1/2 of her wealth to Jason), and eventually ending up with Janet during season 4 until he ultimately ended his existence in the Universe.
- Jason was actually the second of the original four humans to walk through the door. After being directed to the door and being thought to be gone, Jason waited for Janet to return to give her a necklace after Chidi had just walked through the door seconds earlier. Jason then followed Chidi, with his final line being, "Chidi, wait up!"
- During his mortal life on Earth, Michael adopts a dog which he calls Jason, named after Jason himself.
- He does not know how but he has a tattoo on his butt that says Jasom
- Its a surprise to the viewers that none of the characters attempts to harm Jason due to his stupidity grating on their nerves.