Animated movies take years to make, which leaves a lot of time for unexpected surprises along the way. For Tom McGrath, 52, director of DreamWorks Animation’s The Boss Baby, his lead actor, Alec Baldwin, suddenly developed a fresh cultural currency as Saturday Night Live’s Donald Trump. Lee Unkrich, 50, director of Pixar’s Coco, worried about how his young actor’s voice might change during the five-year production. And Chris McKay, 49, director of Warner Animation’s The Lego Batman Movie, “made some people uncomfortable” at the studio when his spooffilled film opened just before the deadly serious Batman v. Superman. But they all agree that’s part of the pleasures and pitfalls of animation, as they talked shop with Nora Twomey, 46, director of GKIDS’ The Breadwinner; Kyle Balda, 46, co-director of Illumination’s Despicable Me 3; and Lori Forte, producer…