The film 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 the film 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.
After Wojtyla accepts the papal election, the cardinals rise and applaud. The camera then pans in towards the new Pope. However, if you look closely, it is actually the mirror image shot from the previous conclave, with John Paul I clearly in the middle of it all instead of John Paul II.
When the newly-elected Pope John Paul II is changing into his white papal cassock, the actor playing the pope switches between Cary Elwes and Jon Voight several times between shots (most likely this scene was filmed twice, once with Elwes and once with Voight, and the scenes were then edited together).
When John Paul gives the Urbi et Orbi blessing after he is elected, there are 16 people standing on the balcony of St. Peter's Basilica. But in the following wide shot from St. Peter's Square, only two people can be seen on the balcony.