This mini-series was approved by the late Pope John Paul II. The project started before his death, and Pope John Paul II was very hands-on with the production and knew of the script. Also, Pope Benedict XVI praised it after watching a screening on November 2005. However, what Pope Benedict XVI saw was a brief cut-down version of Part 1, and all of Part 2, which covers the papacy of Pope John Paul II.
Pope John Paul II was a fan of The Princess Bride (1987), which starred Cary Elwes, who portrayed the young Karol Wojtyla.
Footage of the real Pope John Paul II (albeit with his face obscured) was used for a few scenes, such as the televised meeting with former U.S. President Ronald Reagan, and the pope's historic visit to Israel in 2000. In the latter scene, the real Stanislaw Dziwisz can also be briefly glimpsed as the pope is getting off the plane.
The character of Roman is based on Jerzy Kluger, a Polish Jew and lifelong friend of Karol Wojtyla. Kluger's close friendship with the pontiff is said to have played a key role in helping strengthen Jewish-Catholic relations and influencing the Vatican to officially recognize the State of Israel.
Pope Benedict XVI is briefly depicted in this mini-series as Cardinal Joseph Ratzinger (played by Mikolaj Grabowski).