But, in a rare joint interview with The Hollywood Reporter, the successful Hollywood couple gave a glimpse into how they've become perfect partners in life and work.
"Our feeling was, if we wanted to spend time together, have a life together, then we should just go ahead and make movies together," Susan told the magazine of their reason for starting their production company Team Downey.
Added Robert, "Susan holds one pillar and I hold the other, and this creative arc of tension just flows between us."
Here are five of the biggest revelations from their joint interview:
quicklist:title: Robert Proposed After Three Monthstext: Despite her reservations, Susan agreed to go on a date with Robert. Within three months, he was proposing marriage, even though he wasn't yet divorced from model-singer Deborah Falconer, with whom he has a son Indio. Eventually, Susan agreed to marry Robert but insisted they have a long engagement: two years.
quicklist:title: Susan Laid Down the Law on Robert's Drug Usetext: Susan, who grew up in a Chicago suburb an honor student, had never puffed on a cigarette, much less suffered a drug problem. Whereas, Downey's addiction battle is well known. When she agreed to marry him, Susan insisted that Robert give up drugs completely, and if he messed up, she'd leave. "Addiction was so foreign to me," she told THR. "I was incredibly ignorant of the hold it had on people." Robert replied, "Thank God for that. If she knew the depths of my depravity, we would not be sitting here."
quicklist:title: How Robert Changed Susantext: "I was very focused, driven, rigid, work-oriented," Susan said of her life before Downey. "I didn't care about having a family or making a home. I didn't think about kids. It's not that I didn't want those things, I just didn't think about them. And then I had someone who came in as a tornado, this creative, beautiful ball of insane energy and passion. And it completely opened me up."