Sumi, Kacho, Hyakkan, Goyake and Penpen

"Sumi, Kacho, Hyakkan, Goyake and Penpen" are nicknames for members of R&D1's staff, who were among those credited in the original Metroid under special thanks. It was long thought that their names and those of others (such as “Shikamoto”, or Yoshio Sakamoto) were mistranslations in the localization process. Hirokazu Tanaka clarified in a 2018 interview that these names were actually nicknames of R&D1 workers. "Shikamoto" resulted from Sakamoto residing in Nara, Japan at the time, which features a large population of deer (shika in Japanese). R&D1 staff used to credit themselves using their nicknames rather than their real names. Tanaka did not clarify who Sumi, Kacho, Hyakkan, Goyake and Penpen were. Their real identities remain unknown, as does whether or not they are still part of Nintendo.