Ki Hyun Ryu (Hangul: 류기현) is a television director of animated cartoons. He helped with animation and character design for some of the early episodes of Avatar: The Last Airbender and later returned for The Legend of Korra, directing every episode of Book One: Air. He has also worked as a character designer and supervising producer across all four books.
Ryu's creative insight has been influencing the Avatar franchise for far longer than the beginning of The Legend of Korra: he created the original character designs for Jet, the Freedom Fighters and the foaming mouth guy, contributed to Aang's final design, as well as having animated Aang and Zuko's fight in the latter's cabin during the episode "The Avatar Returns".
Interestingly, Ryu's name has been worded as "Ryu Ki Hyun" by Konietzko on occasion, likely in concern to Ryu's Korean origin; Korean names are spoken in a format that starts with a surname, followed by the given name.
The design of the character Ryu was based on Ki Hyun Ryu.
During The Legend of Korra production meetings, Ryu would typically draw caricatures of his fellow crew members, in particular martial arts coordinator and videographer William Rinaldi. Ryu would later use his drawings of Rinaldi as the character design for the Equalist doorman.