Kang Duk-gu
Kang Duk-gu (강덕구, 姜德九) is a major character in Dae Jang Geum. He is the adoptive father of Seo Jang Geum. Duk-gu is also a Head Chef of the Royal Kitchen (강숙수, 姜熟手). Kang and his wife, Na Joo-daek also have a wine business in Hanyang. Kang and his wife treat Jang Geum like their real child because their two sons died of smallpox, one while Jang Geum was in the palace and another later on when Jang Geum was a slave.
Though Duk-gu is often used as comic relief, he always supports Jang Geum in whatever she does and is very alert. When the Choi family plots repeatedly against Jang Geum, Duk-gu cunningly spies on the Chois, since the Choi family estate and businesses are very near the Kang home and business. Kang's spying pays off when he reports valuable information to Jang Geum, who in turn reports it to the internal affairs officer Min Jung-ho.
Trivia
The role of Kang Duk-gu was played by the actor Im Hyun-sik (임현식, 林玄植). Kang's silliness is portrayed in the song Duk-gu on the Dae Jang Geum soundtrack.