There are plays, and then there’s “Hurlyburly” – a 150-page doorstop of a drama. Clocking in at three hours, it’s a marathon of monologues, especially for its four male leads.

Matthew Rauch should know: He’s understudying all of them.

“It’s the ultimate theater roller-coaster ride,” the 36-year-old told The Post. “To be honest, there were at least five minutes a day where I’d have a severe moment of panic. I’d be on page 30 and think, Holy s–t, I have 120 pages to go!

“But slowly, slowly, I got there.”

At least he has a precedent: Twenty years ago, when “Hurlyburly” played Broadway – with William Hurt, Christopher Walken, Harvey Keitel and Jerry Stiller – an actor named Kevin Spacey did the same thing.

As soon as he was cast, Rauch said, he bought several packs of highlighters, marking each guy’s part with a different color.

Though Eddie (Ethan Hawke’s role) has the most lines – he’s rarely off the stage – Rauch’s biggest challenge was Artie, the older, Jewish writer played by the froggy-voiced Wallace Shawn.

“The last thing I want to do is some Wally Shawn imitation, so I’ve come up with a different characterization – a little meaner, a little more aggressive,” Rauch says. “Nobody’s gonna believe I’m 20 years older than these guys, and I’ve sorta figured out a way to make that work.”

And if two actors get sick the same night? “I hate to put it this way,” he says, “but that’s the theater’s problem.”