Christian Navarro had to learn to drive and get his license before filming started to be able to drive the red Ford Mustang seen in the series.
Jay Asher was inspired to write the book when a family member tried to end their life through 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.
Tony's (Christian Navarro) cross tattoo on his wrist contains a semicolon, which is the symbol for depression and suicide awareness.
Katherine Langford (Hannah) purchased a piano while staying in San Rafael, California during filming. She would play it to help comfort herself between takes when feelings would become overly intense.
Author Jay Asher was fine with the differences between the book and Netflix series, stating "the message is what matters most."