On November 8th, 2017, Sony and the film's production team unanimously opted to replace Kevin Spacey as J. Paul Getty with Christopher Plummer. The decision was made just over a month prior to the December 22nd wide release. This was the second time Scott was faced with drastic re-shoots during his career. He had previously almost had to abandon Gladiator (2000) due to the untimely death of Oliver Reed.
The reshoots needed to replace Kevin Spacey with Christopher Plummer took eight days to film at a cost of $10 million. It also involved Mark Wahlberg and Michelle Williams having to return to the Rome set during the Thanksgiving holiday of 2017.
When the project was in development Angelina Jolie was offered the lead female role of Gail Harris, the mother of John Paul Getty III, but declined. When the project was officially announced, Natalie Portman had been offered the Gail Harris role. However, she had to decline as she was expecting her second baby. Michelle Williams was finally cast.
Christopher Plummer claimed he was prepared to replace Kevin Spacey as J. Paul Getty on short notice because he had previously been considered for the role and had read the script. He had less than two weeks to memorize his lines.
After Kevin Spacey was replaced by Christopher Plummer, director Ridley Scott decided not to show Plummer any footage of Spacey in character, or even tell him how Spacey played the scenes. When finished, Scott found both performances to be quite different and equally effective in their own particular styles.