Jay Asher was inspired to write the book when a family member tried to commit suicide. Some of the events that happen to Hannah are events that happened to teen girls in real life. He interviewed his wife and female colleagues for things that were hard or things they have never gotten over.
Shooting was so difficult, they had therapy dogs visit the set. The series covers many heavy issues, including depression, suicide, and sexual assault, to name a few, so naturally the stars would need cheering up every once in awhile. "I know there was one scene, I wasn't around, but they had therapy dogs on set. There was a puppy per hour," Dylan Minnette recalled in a recent interview.
Neither Katherine Langford (Hannah) nor Dylan Minnette (Clay) had read the book "Thirteen Reasons Why" before being cast to star in the series. Langford read it in between being cast and filming, but Minette didn't want to confuse the character in the book with the character in the show, so he didn't read it.
Kate Walsh did a lot of prep to get into her role. She tried to make her performance as Hannah Baker's (Katherine Langford) mother as honorable as she could. "I spoke to two parents that had a child that died by suicide and I spoke to a psychiatrist, who deals with family therapists, but particularly with families that lost someone in the family to suicide," she told E! News.
The New Zealand Office of Film and Literature Classification created a new certificate (rating) of RP18 (restricted to persons under 18 unless accompanied by a parent or guardian) specifically for the series.
After reading the book the series is based on, Selena Gomez, along with her mother Mandy Teefey and producer Kristel Laiblin, brought the book to producing company Anonymous Content for a screen adaptation. Gomez was previously attached to star in the project back in 2012 when it was still set up as a film at Universal.
After wrapping production, Selena Gomez, Alisha Boe (Jessica), and Tommy Dorfman (Ryan) all got matching tattoos on their forearms of a subtle black semicolon, which represents and symbolizes mental health awareness and suicide prevention.
The character of Skye (Sosie Bacon) is a amalgamation of two people from the novel, a friend of Clay's named Skye, who is a social outcast, and an unnamed Coffee house waitress, who knows Clay but Clay does not remember.
Selena Gomez was originally attached to earlier film attempts as early as 2011, however after multiple delays she had grown too old for the role and thus serves as an executive producer for this project.
Ross Butler was cast in the show Riverdale (2017) at the same time. When season 2 for both shows were announced, he felt doing 2 shows at once was too much and dropped out of Riverdale (2017) so he could focus mainly on 13 Reasons Why (2017).
The show filmed high school exteriors (and some interiors) at an actual high school in Sebastopol, California, called Analy High School. Like real-life Analy, Liberty High School shares the same mascot, the Tigers.
Every time Clay (Dylan Minnette) is thinking of Hannah (Katherine Langford) and there is a flashback, the scene is brighter than in regular time in the show . This has been done to signify that she is the light of the show and when she is not on camera the scene is a lot darker, signifying the unhappiness that's in the scene.
Dylan Minnette (Clay) had a dialogue with producer Brian Yorkey from the get-go about what songs should be on the soundtrack. "I love that he was so open and it was very much a collaboration. There are so many artists on the soundtrack that I'm so proud of. And Clay's room is filled with posters of my favorite bands. There are other artists that I would love to have in there, but they aren't artists that I feel Clay would listen to."
The name Clay has symbolic meaning because in the story he will continue to be reshaped in many ways, just like Clay (Dylan Minnette). By telling her story, Hannah Baker (Katherine Langford) "bakes" Clay into the person he becomes.
Although Selena Gomez was an executive producer, she was only on set for the last day of filming because she was also on a world tour at the time. In an interview, Dylan Minnette (Clay) and Katherine Langford (Hannah) said she was very involved through email the entire filming process, and when she arrived for the last day, it was like she had been there the whole time.
Interiors for the school classrooms and hallways were filmed on-location at an actual school for the first two episodes, until the show's Set Construction crew could catch up. For the remainder of the show, school interiors were filmed in an exact replica of Analy High School built on a soundstage, to accommodate easier filming logistics.
Kate Walsh and Dylan Minnette have both played characters on the show Grey's Anatomy. Kate Walsh played Dr. Addison Montgomery-Shepherd, whereas Dylan Minnette played a young child who needed an ear replacement transplant.
Towards the end of the season 1 finale (13 Reasons Why: Tape 7, Side A (2017)), a song by Selena Gomez is played in the background. Selena Gomez is an executive producer for this show and was originally cast as Hannah when the project was a movie from Universal.
Dylan Minnette (Clay) has played a character named Clay twice (Saving Grace (2007), and 13 Reasons Why) and has been in three different acting roles where his character interacted with a character named Hannah (Awake (2012), Goosebumps (2015), and 13 Reasons Why).
The trivia items below may give away important plot points.
The author (Jay Asher) considered Hannah (Katherine Langford) surviving the suicide but ultimately changed his mind, thinking the original darker ending had more of an impact, and would help raise awareness for suicide.
The book which the series is based on, Jay Asher's "Thirteen Reasons Why", focuses almost solely on Clay's personal experience listening to the tapes, and his feelings about what he hears. He does not seek revenge on the students Hannah blames for her suicide, and there is no lawsuit, or full storyline about the Baker family. Also, he only realizes Tony is the one who has the other set of tapes when he, Clay, is going to stop listening before hearing his own, and Tony intervenes, exposing himself, in order to get him to keep listening; it does not occur near the start of the story, like in the series; it's a surprise reveal.
In episode 1.8, 13 Reasons Why: Tape 4, Side B (2017), near the end of the episode when Clay (Dylan Minnette) is looking for his old copy of the school zine in lost and found, you can see a book on his shelf titled "Broken Symmetry." Broken symmetry is a physics term which describes a phenomenon in which small fluctions to a system ultimately decide its fate. This also describes Hannah's (Katherine Langford) story and how everyone's actions, or inactions, lead to her decision to commit suicide.
In the book, Hannah (Katherine Langford) commits suicide by overdosing on pills. In the show, she gets into a full tub, fully clothed, slits her wrists, and bleeds to death. The crew filmed it like this to send a clear message about suicide prevention.
At the beginning of the series when Clay (Dylan Minnette) is first listening to the tapes, Mr Porter (Derek Luke) asks what he's listening to. His reply is 'Ultravox'. In the last episode when Hannah (Katherine Langford) leaves Mr Porter's office, "Vienna" by Ultravox is played.
It is implied Alex (Miles Heizer) shot himself and he also complained about stomach pains. This mirrors Kurt Cobain, who committed suicide by shooting himself and had similar undiagnosed stomach pains.
The order of the tapes is slightly different in the book. Alex is #2 and Jessica is #3, they are the reverse on the show. Clay is #9 (11 on the show), followed by Justin #10 (9 on the show) and Jenny Kurtz #11 (10 on the show and the character's name was changed to Sheri Holland). Most of the story points are the same with the exception of Courtney Crimsen (Michele Selene Ang), whose story is completely different from the novel.
The character of Jeffrey (Brandon Larracuente), the senior Clay (Dylan Minnette) tutors, does not appear in the novel. In the novel, the senior involved in the car crash during Sheri's (Ajiona Alexus) tape (Jenny in the novel) is unnamed and has no past friendship with Clay.
In the beginning of the first episode, 13 Reasons Why: Tape 1, Side A (2017), after Clay (Dylan Minnette) accepts Tony's (Christian Navarro) offer for a ride home, Tony asks Clay if he can play him a cassette tape. In the novel, Tony uses this ploy with everyone else, prior to Clay, who's on the tapes in order to gauge if they've listened to them or not. This scene, between Tony and Clay, is not in the novel. In the novel Tony realizes Clay has the tapes after Clay steals his walkman. During the episode, as Clay reacts normally when shown the cassette tape, Tony knows Clay hasn't listened to the tapes yet.
Timothy Granaderos (Monty) received death threats after his character commits a horrendous sexual assault on Tyler Down. This prompted his co-stars (including Devin Druid (Tyler)) and fans to come to his defense and start the hashtag #timisnotmonty.
In the novel Tape 4, Side A, instead of leaving a note to Zach Ross Butler as in the show, Hannah instead takes her bag off the rack and reattach it with a tiny piece of duct tape, and as Zach reaches for her note, the bag falls off.