The 38-year-old actor opened up about his chemistry with Mirren in a behind-the-scenes look at the drama.
"We have really great chemistry. We were like fire and a dry house," Reynold's said. "It was evident from the get-go.
"She's even my next-door neighbor in our hotel," he added. "And I'll occasionally hear her whack on the wall for me to keep it down [when I'm] singing some Tina Turner at the top of my lungs."
In April, at a screening of Woman in Gold, Reynolds and Mirren walked the red carpet together, and they two seemed to have a wonderful time.
"Should I be concerned that my husband's never looked at me this way?... #WhereAreThoseEyesWanderingReynolds" Lively joking captioned the well-timed photo.
To her credit, Lively also tagged the pic with the most accurate hashtag ever: #HelenMirrenIStheSexiestWomanAlive
Clearly, their chemistry is something real.
Check out the video to hear more about Mirren's
work in Woman in Gold
, available on DVD July 7.