It is generally inferred that the prototype of Prince Li Ke is Gyeongjong Li Yun (1688-1724). He was the 20th generation monarch of the Li family of Korea and reigned from 1720 to 1724.
Reasons:
1. The plot explains that time travel occurred 300 years ago, and the Crown Prince is 25 years old, so the Crown Prince’s age is calculated as fictitious years, and his birth year should be 1688. It happened to be the year Jingzong was born.
Moreover, Jingzong ascended the throne in 1720, and he became the crown prince at the age of 25.
2. In the second episode, when they were locked up in the police station, they were asked their birth dates. The results were Gengwu, Xinwei, and Wuchen years. 300 years ago, these three years corresponded to 1690, 1691 and 1688 respectively. They were similar in age to the crown prince, which supports the theory that the crown prince's prototype is Jingzong.
3. Jingzong in history only reigned for 4 years, died young and had no heirs. Only in this way can his soul travel back to Tai Rong after his death, as explained in the ending.
4. The real historical materials about Jingzong are also reflected in the plot.
Historical data 1: According to historical records, Jingzong’s biological mother was Zhang Xi’s concubine, who was very powerful during the Suzong era. In the twenty-seventh year of Suzong’s reign (1701), Xi’s concubine Zhang was sentenced to death, and the ministers were worried. After Gyeongjong ascended the throne, he would seek revenge for his mother's death just like Lord Yeonsang, so he once requested that he be crowned the heir apparent.
This historical data is very consistent with the conversation between the prince and the rebel minister in the last episode of the plot.
Historical data two: Regarding the cause of Jingzong’s death, according to the "Records of Yeongjo", on January 16, the third year of the reign of King Yeongjo (Jingzong’s younger brother, Yeonjongjun), on the way to worship the rebels at Jingzong’s mausoleum, Someone Li Tianhai publicly accused King Yeongjo of Shijun, saying that Kingyeongjo poisoned King Jingzong with poisonous crabs in soy sauce through the kitchen of Queen Inwon's back palace; or it was because King Jingzong violated the medical theory of food incompatibility and ate crabs at the same time. Although he was not feeling well due to eating soy sauce and persimmons, Lord Yanreng still served Jingzong ginseng tea despite the objections of doctors. As a result, Jingzong's condition worsened and he died.
This historical data is completely consistent with the explanation in the play that the prince cannot eat crabs with soy sauce.
Historical fact three: Jingzong married two princesses. The first one was consecrated as a concubine in the 22nd year of Suzong (1696), and on February 7th in the 44th year of Suzong (1718) He died on the same day at the age of thirty-three.
This historical data shows that before Jingzong ascended the throne, his imperial concubine passed away, which is consistent with what the plot tells.
5. After Jingzong’s death, the Qing Dynasty granted him the posthumous title of King Kegong. This can also be seen as the reason why the crown prince was named Li Ke in the play.