There has been a fairly strict separation of the DC film and television world. How were you able to combine the two with Miller’s cameo?


We were series wrapped on “Arrow,” and we were wrapped on the whole crossover. We were in post and some episodes were locked, and some were soft-locked. I got a phone call from [Warner Bros. boss] Peter Roth saying, “I know you’re locked, but can you put Ezra into the crossover?” And I said, “Yes.” And he said, “How, you’re series wrapped? And you’re wrapped on the crossover.” And I said, “Yeah, I know, but if you’re telling me Ezra Miller can be in the crossover, I can make it happen.” I called Eric Wallace who who is the showrunner of “Flash,” and he called up Grant Gustin — because the one thing that was our only concern was the thought we didn’t want to do it unless Grant was 100 percent on-board with it. And he was. He was incredibly enthusiastic and on-board with it. And then we got on the phone with Ezra Miller and told him the scene I had written and he was completely into it. And we just went. We put together a unit of the “Flash” crew on the “Flash” set [since “Arrow’s” team, which had produced the rest of the hour, was gone]. And much to our surprise, no one noticed Ezra Miller was in Vancouver and no one leaked it from the crew, which we appreciate. So we were able to keep it a surprise.