Northrop YB-49 prototype jet-powered heavy bomber was initially chosen for the image of the Eva transport aircraft, but the crew later decided to use the North American XB-70 Valkyrie. Eva-01 was intentionally represented while chasing the Jet Alone in the same scene. In reality, the Eva would have to stumble forward, but the staff wanted the flow to be more fluid, creating a scene in which the Eva chases the other mecha. The episode also contains homages to the animator Kunihiko Ikuhara, a friend of the director Anno, and Kihachi Okamoto, of whom it takes up various directing techniques. Koichi Yamadera, Hiro Yūki, Tetsuya Iwanaga, Tomokazu Seki and Megumi Hayashibara, voice actors of several main characters in the series, played unidentified characters for "A Human Work", including announcers and Shinji's unnamed classmates. A four-beat Jazz version of Fly Me to the Moon sung by Japanese singer Yoko Takahashi was used as the ending theme. Cultural references and themes In the first scene Gendo is framed in his office and the Tree of the Sephiroth, a diagram of the Jewish Kabbalah, is visible on the ceiling of the room. The ceiling illustration of Commander Ikari is taken from Athanasius Kircher's Oedipus Aegyptiacus. According to MCC Agora, some of the discernible Hebrew words of the diagram translate to "thunder" and "God", a possible link to the Angel Ramiel, defeated in the previous episode, which name means "thunder of God". Slant Magazine Micheal Peterson noted that Gendo's position at the desk "is in relation to the Godhead symbol on the tree". In the same scene, a text that mentions apoptosis and apobiosis, terms of molecular biology, is framed. A few scenes later, a school text by Shinji with fictitious, manipulated details on Second Impact and revelations on First Impact is framed; the informations constitute a reference to the Giant-impact hypothesis. Japanese architect Yasutaka Yoshimura regarded SSTO's interior visible in the previous scenes as a possible reference to a spacecraft visible in the movie 2001: A Space Odyssey (1968), while Jet Alone's name comes from the robot Jet Jaguar, appeared in the special effects film Godzilla vs. Megalon (1973) and originally called "Red Alone". The episode's pivotal theme is interpersonal communication. In "A Human Work", the psychology of Shinji, who finishes the first part of his path in the episode, and of Misato is deepened. At the center of the episode are the different