"Hospital Playlist" director Shin Won Ho and screenwriter Lee Woo Jung not just delivered heartwarming and remarkable moments in the top rating medical K-drama series but managed to entertain the viewers with surprising cameos.

There's no denying that the production team had an incredible casting lineup featuring lead stars Jeon Mi Do, Jo Jung Suk, Kim Dae Myung, Yoo Yeon Seok, and Jung Kyung Ho; however, PD Shin Won Ho and the rest of his team wanted to give the audience a hint of nostalgia from his previous works.

From the mega-hit "Reply" series to the beloved "Prison Playbook," the team wowed the audience with brief stints from well-known stars.

Given "Hospital Playlist 2" episode 10 will be delayed for another week, here's a look back at the cameos that you might have missed in the tvN's medical drama.

READ MORE: 4 Surprising Developments Seen on 'Hospital Playlist' Season 2

Go Ara as Herself

The former model turned actress Go Ara played Lee Ik Jun's (Jo Jung Suk) famous ex-girlfriend in the first season of "Hospital Playlist" and made a special appearance in episodes 5 and 6.

In one scene, Ik Jun recalled why she and Go Ara broke up. He explained that she was very picky with food and was conscious about her figure.

Years later, she unexpectedly saw her ex at Yulje and invited him to grab lunch. However, Ik Jun witnessed how Go Ara changed through the years and teased her for being a big eater.

Prior to her cameo in the medical drama, Go Ara was also the OG cast of "Reply 1994."

Sung Dong Il as Father Peter

From another "Reply" series is Sung Do Il, who played Ahn Jung Won's (Yoo Yeon Seok) older brother Peter in "Hospital Playlist."

The veteran actor appeared in both seasons, portraying one of Jung Ro Sa's sons who chose to be a priest. In the drama, he constantly tells Jung Won not to consider entering the seminary but rather continue his career being a doctor.

Choi Moo Sung as The Patient's Husband

PD Shin Won Ho casted Choi Moo Sung as the patient's husband who owns a shop at Ssangmun-dong called Phoenix.

"Prison Playbook" fans would recognize him as cell leader Kim Min Chul, Je Hyuk's cellmate in the Penitentiary detention.

In the medical K-drama, Choi Moo Sung was spotted offering Ik Jun a special gift as a thank you for saving his wife.

Lee Kyu Hyung as Yoo Han Yang

Probably one of the beloved characters in "Prison Playbook" is Lee Kyu Hyung, who played the extremely intelligent Loony.

The versatile actor surprised the viewers when he made a special appearance as Gyung Jin's brother in "Hospital Playlist 2" episode 3.

What's interesting about his role is his on-screen mother is insisting him to date the neurosurgeon Chae Song Hwa, played by Jeon Mi Do.

Yoo Jae Myung as Shin Sung Eui

Joining the "prison Playbook" cast who appeared in "Hospital Playlist" is Yoo Jae Myung, who made a cameo in the medical drama as Shin Sung Eui, Department of Radiology professor.

In the drama, he was Ik Jun's strong contender during Yulje's badminton match; however, in the 2017 comedy-drama, Yoo Jae Myun played Kim Je Hyuk's lawyer.

KDramastars owns this article.

Written by Geca Wills