Warning: SPOILERS ahead for Steven Spielberg's Ready Player One, as well as Ernest Cline's original novel! Read ahead at your own risk!
Steven Spielberg's Ready Player One is an ode to anything and everything that geeks love from the 1980s, except for the work of Spielberg himself. The film intentionally steers clear of its own director's films, but that doesn't mean that Spielberg didn't consider using one specific reference. In fact, the director recently opened up in an interview and admitted that he almost considered paying homage to Ernest Cline's novel and his own work on Indiana Jones and The Last Crusade by having Wade Watts use a "Grail diary." Spielberg explained:
The only thing I was really close to putting in, because it's so prominent in Ernie's book, because it's where Wade keeps all of his notes, was something called the Grail diary. Which was a diary kept by Sean Connery in the third Indiana Jones movie, The Last Crusade. And so the thing I was closest to putting in was giving Wade's character the Grail diary.
So while there aren't many overt references to Steven Spielberg movies in Ready Player One, the Grail diary from the book almost played a massive role in the film. In the book, it's what Wade Watts uses to keep track of his information regarding James Halliday's Easter egg and plot his strategy to win the contest. In the context of Spielberg movies, the Grail diary is the book kept by Sean Connery's Henry Jones Sr. to keep track of all of his information on the Holy Grail. It likely would've been easy to include in the film, but Spielberg ultimately decided to keep it out of his adaptation, which has me wondering if that was a way of getting back at Ernest Cline for his digs at Indiana Jones in the book.
It definitely would make perfect sense for Steven Spielberg to include a nod to the Grail diary in Ready Player One, per the director's recent remarks to USA Today. The Indiana Jones version of the book is considerably important in the search for the Holy Grail, and Indiana Jones ventures to Berlin to prevent it from being incinerated. In fact, he even gets it autographed (unintentionally) by none other than Adolph Hitler.