The reason Charlize Theron almost didn’t star in Monster

Aileen Wuornos was a former Florida prostitute, who was executed in 2002 at age 46 after being convicted for murdering six men. She was the 10th woman put to death in the United States since the death penalty was reinstated in 1977.

Charlize Theron, who gained 30 pounds and wore facial prosthetics for the part, admitted to SplicedWire that she wasn’t familiar with Wuornos or her story before signing on to star in Monster. “This was the first time, I think in my entire career when by the second-to-last page [of the script], I still didn’t know how I felt about the character,” she said. “I also thought it was interesting because I don’t think it’s really a common thing for writersto write conflicted female characters.”

The actress also said that she read that Wuornos never removed her shirt, even when prostituting herself, and that was part of why she put on weight for the part — to embody the murderer’s insecurity and “scars” about her own body.

Theron isn’t the only star who went to great lengths for a role. These stars also went to extremes for their art.