Cross-references

Reference to Hot Stove League and wondering why there isn't a second season in episode 4.

Namkoong Min as Chun Ji-hoon from One Dollar Lawyer cameo

Multiple references to CLOY and the leading actors.

Song Joong Ki as Vincenzo and Jeon Yeo Been as Hong Cha Young from Vincenzo cameo.

Reference to Signal

Lee Min Ki and Jung So Min played Kim Mi So's parents when she was little.  They were the leading actors in Because This is My First Life.

Kim Soo Hyun cameo as Bang Dong Gu from the movie Secretly Greatly.

Choi Moo Sung and Kim Sun Young, playing their characters from Reply 1988.

Reference to Goblin

Reference to Saja Boys from K-pop Demon Hunters.  Kang Woo-Seong says that people think Gold Boys are an animated group.

Reference to Kim Soo Hyun's series Love From the Stars when Moon Gang Tae tells Ko Mun Young that he does not have a passport, and she asks him if he is from another planet. (ep. 9) 

Reference to Dr. Romantic and Hospital Playlist (Ep 1)

Lee Gang Pung [Ghost]: You should be called Attorney Romantic.  Did you graduate from med school too? What a playlist.

FL pretending to be prosecutor Kang Ha Na which was her character in Taxi Driver 

ML, Tae Hui, is going to teach the FL, Dong Ju, who is played by Lee Hye Ri, to swear just like her character did in Reply 1988 when Deok Sun taught Taek to swear.