Taika Waititi discovered in his research that WWII Germany was very vibrant and fashionable and was interested in shying away from traditional war films that presented it as dark and dreary. He opted, instead, to present the city as a celebratory place on the surface and dressed the characters as stylishly as possible. He liked the idea that everything seems happy, but just underneath the surface "the third Reich is crumbling, and, you know, the dream is over."
When Taika Waititi, who is Maori/Jewish, was asked about why he chose to play the role of Adolf Hitler, he said "The answer's simple, what better 'fuck you' to the guy?"
Taika Waititi has known Thomasin McKenzie (Elsa) since she was "very, very little" as he's friends with her parents, from New Zealand's theater scene. He tasked her with watching हेदर्स (1989) to give her the vibe he was looking for with the character.
Taika Waititi described the film as a love letter to his mother, and single parents everywhere: "It wasn't until I was a grown up and I had kids of my own that I realized 'oh, these parent people, they make a lot of sacrifices, it's really hard raising a kid!'"
The various military decorations that Captain Klenzendorf wears in the film indicate that he's a heroic combat veteran and not just some administrator or incompetent who's been assigned to babysit the Hitler Youth, to get him out of the way. He has both the Iron Cross 1st and 2nd class (both awarded for personal acts of heroism), a bronze close combat clasp (signifying that he's fought in a minimum of 15 hand-to-hand engagements), a silver tank destruction badge (awarded for individually destroying an enemy tank with a hand-held weapon), and a gold wound badge (meaning that he's been wounded in combat at least 5 times).