Playwright Theresa Rebeck’s newest off-Broadway offering, The Understudy, is pretty clear regarding what the show is about (um…an understudy). But what you might not know is just how funny the new comedy is, or how much fun Tony Award winner Julie While, Emmy Award nominee Justin Kirk and television star/stage newbie Mark-Paul Gosselaar are having bringing this valentine to the theater to life. We checked in with the trio of leading players at Roundabout Theatre Company’s Laura Pels Theatre to get some starry details about the new production, its talented playwright and director and what it’s been like to go onstage nightly as The Understudy’s lone players.