Pemeran Happiness

Han Hyo Joo

as Yun Sae Bom

Pemeran Utama

Park Hyung Sik (박형식)

as Jung I Hyeon

Pemeran Utama

Jo Woo Jin

as Han Tae Seok

Pemeran Utama

Lee Joon Hyuk

as Kim Jeong Guk

Pemeran Pembantu

Park Joo Hee

as Lee Ji Su

Pemeran Pembantu

Baek Hyun Jin

as O Ju Hyeong

Pemeran Pembantu

Moon Ye Won

as Woo Sang Hui

Pemeran Pembantu

Park Hyung Soo

as Kook Hae Seong

Pemeran Pembantu

Jeong Un Seon

as Sin So Yun

Pemeran Pembantu

Song Ji Woo

as Park Seo Yun

Pemeran Pembantu

Bae Hae Seon

as O Yeon Ok

Pemeran Pembantu

Cha Soon Bae

as Seon U Chang

Pemeran Pembantu

Han Joon Woo

as Kim Se Hun

Pemeran Pembantu

Park Hee Von

as Na Hyeon Gyeong

Pemeran Pembantu

Na Chul

as Na Su Min

Pemeran Pembantu

Lee Ju Sil

as Ji Seong Sil

Pemeran Pembantu

Hong Soon Chang

as Kim Hak Je

Pemeran Pembantu

Kang Han Saem

as Kim Dong Hyeon

Pemeran Pembantu

Kim Young Woong

as Ko Se Gyu

Pemeran Pembantu

Lee Ji Ha

as Ji Mun Hui

Pemeran Pembantu

Lee Ju Seung

as Andrew / Choi Jong Wook

Pemeran Pembantu

Isle Han

as Lee Bo Ram

Pemeran Pembantu

Nam Mi Jung

as Lee Deok Sun

Pemeran Pembantu

Joo Jong Hyuk

as Kim Seung Beom [Seyang personal trainer]

Pemeran Pembantu

Nam Sang Woo

as Lee Jong Tae (Ep. 1)

Bintang Tamu

Kim Yeon Woo

as Il Ho (Ep. 1)

Bintang Tamu

Han Sa Myung

as Seong U Je (Ep. 1)

Bintang Tamu

Park Sung Il

as [Seyang High teacher] (Ep. 1)

Bintang Tamu

Choi Yi Sun

as [Motel clerk] (Ep. 1)

Bintang Tamu

Seon Yul U

as [Detective, Seyang Police Station] (Ep. 1)

Bintang Tamu

Yoo Tae Joo

as [Guard post soldier] (Ep. 1)

Bintang Tamu

Lee Kyu Hyung

as Lee Seung Yeong [Special ops unit] (Ep. 1-3, 8, 12)

Bintang Tamu

Baek Sung Chul

as [Reporter] (Ep. 2)

Bintang Tamu

Yoon Sang Won

as Kang Ju Heon [Trainer] (Ep. 2-3)

Bintang Tamu

Kim Shi Heon

as [Paramedic] (Ep. 3)

Bintang Tamu

Park Chul Min

as [Anchorman] (Ep. 3)

Bintang Tamu

Lee Ki Young

as Choi Seok Ju [Atum Therapeutics Chairman] (Ep. 3-4, 7-9)

Bintang Tamu

Kim Joo Yeon

as Kang Eun Ji

Bintang Tamu

Lee Dong Gyu (이동규)

as [TNBC anchorman] (Ep. 4)

Bintang Tamu

Jeong Min Sung

as [Bulding #102 resident] (Ep. 4-7)

Bintang Tamu

Park Hui Eun

as [Resident] (Ep. 5)

Bintang Tamu

Park Ki Ryung

as [Prime minister] (Ep. 5)

Bintang Tamu

Yoon Bok Sung

as [Politician] (Ep. 8)

Bintang Tamu

Lee Seung Jun

as Kim Tae Yun [Brigadier general] (Ep. 12)

Bintang Tamu

Ahn Ji Hwan

as An Guk Jin

Bintang Tamu

Sun Young Uk

as [Seyang Forest Le Ciel security guard]

Bintang Tamu

Jung Hyeon Ok

as [Infectee]

Bintang Tamu

Kim Tae Seong

Composer

Ahn Gil Ho

Sutradara

Steve M. Choe

Editor

Han Sang Un

Screenwriter