The 1982 play “The Real Thing” has a reputation for being the accessible one in playwright Tom Stoppard’s brainy canon. But take it from the cast — including Ewan McGregor and Maggie Gyllenhaal — of the current Broadway revival: It’s still a challenge.

“It’s much trickier to do than it is to read,” said McGregor after the Roundabout Theater Company’s opening night perf Oct. 30. “Which isn’t always true, but I suppose it’s always true of the great ones.”

Josh Hamilton (“American Horror Story”) came to the show after previously appearing in the 2006-07 staging of Stoppard’s three-play epic “The Coast of Utopia.” “This one isn’t about physics or Russian history, so I thought: This one’ll be easier, it’s a romantic comedy!” he said. “But no. It’s no less Escher-like in its construction. Everything means ten things and refers back to ten other things.”

For Cynthia Nixon, it’s her second time around with the play. As a young actor she appeared in the play’s 1984 Broadway bow, playing another role. “I loved all the jokes when I was a kid,” she recalled, “All the tricks and the intricacies of the plot. Now I see it’s so timeless about love and infidelity and pain.”

Gyllenhaal also circled back to the play, after reading it “blew my mind” when she was 17. It still blows her mind, but in a different way. “I had no idea what it fucking meant when I was 17!”

All four of them found themselves singing in the production — something some of them never thought they’d do in public. Credit director Sam Gold for that.

“I don’t know, he talked to us about the theme of the play and he had us sing every day at the start of rehearsal,” Nixon said. “He sort of tricked us into it.”