Esther Earl

At the age of 12 in November 2006, in Marseille, Earl was diagnosed with metastasized papillary thyroid cancer. The following Thanksgiving in 2007, her parents sought a second opinion at Boston Children's Hospital. Earl's doctors informed her and her parents that her cancer was terminal.

In 2007, Earl met John Green and, Margaret Talbot of The New Yorker states, "was one of the earliest nerdfighters." Initially the two maintained an online friendship, which grew from her self-identification as a Nerdfighter, a member of Nerdfighteria, the online community of Vlogbrothers fans. Earl developed her friendship with Green upon meeting him at LeakyCon 2009, a Harry Potter conference. Following the conference, she would continue in the Nerdfighter community, including her involvement with the Harry Potter Alliance (HPA) and their winning of a $250,000 grant, after Green encouraged voters to vote "with Esther" for the HPA.

She continued her online community activities until her death due to thyroid cancer on August 25, 2010. John Green, saddened by Earl's death, dedicated a eulogy in vlog format titled, Rest in Awesome, Esther. Earl's YouTube videos remained available for streaming following her death.

Esther Earl inspired the character Hazel Grace Lancaster in Green's 2012 novel, The Fault in Our Stars, as well as its 2014 film adaptation. Shailene Woodley portrayed Lancaster in the novel's film adaptation. Although Earl inspired the novel and the character of Hazel Grace, the novel is not intended to be biographical. Green dedicated the novel to Esther but also found inspiration through others, including his son and wife, as well as his experience as a children's hospital chaplain. Green wrote on his Tumblr blog, "I don’t want people conflating Esther with Hazel (they’re very different), and it’s extremely important to me that I not claim to be telling Esther’s story."

Following her passing, Earl inspired communities she participated in such as Nerdfighteria and the Harry Potter Alliance. She inspired two books, "Esther Day", as well as the founding of a nonprofit organization. In 2014, after the release of the film adaptation of The Fault in Our Stars and Esther's novel, Esther's parents spoke at Wallace State Community College, as well as the Dana–Farber Cancer Institute about the legacy that Esther left behind. In 2015, Alba, a Quincy restaurant, held a Summer Gala fundraising event in her honor.

Shortly before her death, Green uploaded I Love Hank: Esther Day 2010. The video was uploaded in celebration of "Esther Day", a day which Earl stated she wanted to be about "family and love." Esther Day is celebrated annually on August 3, coinciding with Esther's birthday. Green has stated Earl was the one to suggest "the idea of celebrating friends and family and love," specifically, "the kinds of love that are too often overlooked in our culture: love among friends and family." In 2014, bookstores around the United States celebrated Esther Day. Additionally, Green has called Esther Day, "the most important holiday in Nerdfighteria."