Inzaghi was based on a real pigeon living outside of the writer's office.
Hong Cha Young's father, Hong Yu Chan, has 4 plants in the Jipuragi office and its all named after Song Joong-ki's character in some series that he played. It is Maru, Pungho, Sijin, and Eunsom. The writer said it was his/her idea to put Joong-ki's past character name. Joong-ki even said that the writer adores him so much.
Kim Yeo-jin (Choi Myung Hee) and Choi Deok-moon (Tak Hong Shik) were both in Rookie Historian Goo Hae-Ryung (2019).