Julia Roberts had one requirement to join Starz's Gaslit: Casting Sean Penn

Variety

“I didn’t ever think we’d get her but her one requirement was that she act with Sean Penn. You didn’t have to twist my arm, but I didn’t say yes right away — I had to eat dinner with him,” Gaslit creator Robbie Pickering told Variety at last night's premiere. “I was so nervous I showed up in this leather jacket that I shouldn’t have been wearing. But I was like, ‘Sean Penn is a tough guy! I have to look cool.'” Once they were on set, Roberts and Penn's chemistry was very apparent. “They know each other so well, they have a very deep love for each other,” says Pickering. “You’re really seeing two people who know each other — they’ve known each other for decades.” ALSO: Roberts was stunned when Penn slapped her during a fight scene: "It wasn't a little kiddie soft-paws slap...He gave me such a wallop."