Fancasting the K-Drama version of Accidentally on Purpose

Yoo In Young

South Korean

as Billie

A woman nearing 40's that thought her boyfriend was going to propose but instead dumped her who decided to follow some questionable advice to have a one night stand with a younger guy only to find herself pregnant later. Realizing it might be her last chance to have a baby she decides to keep it against everyones disapproval. Later she  lets the father move in  and as they get to know each other wonders if she should keep him as well. 

Kim Min Jae

South Korean

as Zach

A homeless twenty-four year old inspiring chief who has been struggling working multiple jobs and crashing where ever he can, including his car who has kind of accepted his fate. It doesn't help that the only person he can lean on is his troublemaking best friend Davis. After finding out he's going to be a father and Billie lets him move in, he decides he needs to do better. 

Jin Ki Joo

South Korean

as Abby (Billie's younger sister)

A bored housewife that married and started a family young, and now that her children are in school finds herself getting (willingly) mixed up with Davis's antics and schemes.  Despite everything she still idolizes her older sister. 

Kim Sang Kyung

South Korean

as Nick (Abby's Husband)

A man with ambitions that don't match up to his talent, and has been failing to get on his father-in-law's good side despite being married to his daughter nearly a decade. 

(He also attempts to bond with Zach, but the former thinks he's a little weird so it doesn't always goes over well). 

Lee Deok Hwa

South Korean

as Billie's father

A retired Army general he comes off as stern and uncompromising but in reality he cares more about his daughters then anyone else, and only wants the best for them. He takes a liking to  Zach which baffles his girls since he openly gives his son-in-law a hard time. 

Kwak Dong Yeon

South Korean

as Davis

Zach's longtime best friend who always getting someone involved with some sort of scheme or charade (like pretending to be the cousins of celebrities to get things, accidentally getting everyone involved in pyramid schemes, etc) 

* He was originally a stoner, but considering South Korean views on weed... yeah, I changed him a bit. 

Ye Ji Won

South Korean

as Olivia 

Billie's coworker who  spends most of her nights partying and never  dates anyone for too long and has zero intentions of changing that lifestyle. She's the one who suggests Billie sleeps with Zach when they meet him at the club.