Mireille Enos is an expert marksman in real life, which gave her an edge in the action scenes.
Writer-producer David Farr and Sarah Adina Smith (director of Episodes 1 & 2) talked about wanting to get Karen O to contribute some music to the series. Sarah managed to get David a meeting with the musician. She ended up writing and recording the song "Anti-Lullaby," which was introduced in Episode 1 (for the scene of Erik running through the woods) and is used throughout.
Karen O, who wrote music for the series, can also be heard on the soundtrack as the lead singer of the band Yeah Yeah Yeahs.
Jasmine Breinburg, who plays Girl 217, caught the world's attention when she starred in a dance routine in the London 2012 Olympic Opening Ceremony, directed by Danny Boyle. She stole the show as a girl who loses her phone and dances through 40 years of British music history while pursued by a smitten young man whom she kisses at the end.
Ursula Werner (Sara Heller) was born in Berlin, where she studied at the Berlin State Drama College and joined the famed Maxim-Gorki-Theatre.