Bruce Wayne learned that the mysterious Diana wasn't a normal human in Batman v Superman: Dawn of Justice when he found a photograph of her in Lex Luthor's metahuman files that was taken during World War I. This was the first major tease for the Wonder Woman movie, and over a year later, audiences learned how Diana of Themyscira ended up in that group picture. According to Ewen Bremner, who plays Charlie the sniper in Wonder Woman, that photograph was the first thing shot when the Amazon's solo movie began principal photography. Unfortunately for the cast and crew, this posed challenges when they went back to shoot the events leading up to that moment. According to Bremner:
It meant that when we eventually got around to shooting the scene that the [photograph] is from, we had to really painstakingly recreate it. Because we [took the photo] against a half-built set, in a way sets were still being built at that point. So by the time we came around to filming that scene, probably around five months later, the sets were much more developed. So we had to find a way to recreate the exact same image after half a year had gone by.
Wonder Woman's main shoot kicked off in November 2015, and Batman v Superman: Dawn of Justice was scheduled for release in late March of 2016. So to ensure that the World War I photo could be feature in the second DC Extended Universe entry, director Patty Jenkins had to gather Ewen Bremner, Gal Gadot, Chris Pine, Saïd Taghmaoui and Eugene Brave Rock together to pose before beginning anything else during the production. So taking care of that first was beneficial for Batman v Superman, but as Bremner informed Yahoo Movies, they had to make sure that the recreation of that picture on the completed set looked exactly the same. Looking at the photograph below and the image above, they did an impressive job making sure they matched up nearly perfectly, aside from that strap on her chest being slanted the wrong way.
Warning: SPOILERS for Wonder Woman are ahead!
While no context was provided in Batman v Superman: Dawn of Justice for how Diana ended up in that photograph during World War I, Wonder Woman revealed that it was taken after Diana and her allies successfully liberated the Belgian village of Veld. Diana had already spent some time with Steve Trevor, Charlie, Sameer and Chief, but when the Amazon charged across No Man's Land to take the brunt of the German firepower, they aided her on the battlefield and within the village, subsequently leading the rest of the Allied Forces to join them. After Veld's liberation, the four men remained with Diana, and while Steve Trevor sacrificed his life to prevent Doctor Poison's gas from being delivered, the rest of them lived to see the Great War conclude. A century later, Diana received the physical photograph from Bruce Wayne, and you could tell by her expression that it was an important memento for her.
Wonder Woman is now playing in theaters, and Diana will be back on the big screen for Justice League on November 17.