As a Businessman
Duke Koudou is the president for a Japanese game developing company. He works mostly promoting the company's games around the world, always carrying some AES cartridges, a catalog of new products and a set of memory cards inside his briefcase. However, Duke is a little distracted and usually ends having his briefcase stolen (by the player, as a pickup for some bonus points), making him blame whoever he was talking with. Usually it is some delivery boy, who runs away crying, emotionally scarred for life.
- In both games, he is at the beginning of Mission 1 where he is talking to an Arabian merchant outside of a small house. Sometimes, he is replaced by another merchant.
- In Metal Slug 2, he's at the beginning of Mission 4 where he talks to a delivery kid.
- In Metal Slug X, he shows up in the Final Mission inside the Rebel base standing next to a POW who is tied to a wooden pole. Unlike other instances, Duke doesn't react to his briefcase being missing.
As a Civilian
When not promoting his company, Duke appears in the middle of the battlefield trying to make a conversation. Sometimes, he is randomly seen out in the open (Metal Slug: Super Vehicle-001); other times, he is a reward from a POW (Metal Slug 6 and Metal Slug XX). Duke acts as a collectible item, although he is worth zero points when collected. He disappears if left alone.
- The Doctor is a sprite edit of Duke Koudou.
- Duke Koudou is named after the former president of SNK and executive producer of Metal Slug X, Yoshihiko Koudou.
- Duke Koudou was referred by international fans as "Parker". This fan name was made semi-official in a Steam trading card for the first Metal Slug.
- Metal Slug Steam Trading Card. https://www.steamcardexchange.net/index.php?gamepage-appid-366250
- Neo Geo Freak: Issue 7/1996; pg. 53. http://6th-divisions-den.com/archives/ms_sv001/Neo%20Geo%20Freak%2007.1996/Scans/NGF%2007.1996%20Page%2052-53.jpg