Matthew McConaughey said he shaved his head, gained 45 pounds and wore false teeth to make himself even uglier than usual for the character. He claimed he gained the weight by eating cheeseburgers and drinking lots of beer and milk shakes.
During an interview on ESPN's First Take, Matthew McConaughey claimed this was his favorite role he has ever done.
"Gold" is based on the Bre-X scandal of the 1990's. Bre-X was a Canadian company. The bar where Wells and his company hang out is called "The Three Greenhorns." This is the name of a real restaurant (not bar) in Vancouver, BC, Canada (The Three Greenhorns were, famously, three of the earliest homesteaders in Vancouver). Although the company has been moved to Nevada, the writers kept the name of the restaurant.
Michelle Williams was cast in the lead role but dropped out. Bryce Dallas Howard replaced her after filming had already begun.