Textbook vs Real
Textbook이 사람아i sa-ram-a
Real이 자식아i ja-sik-a
Why Koreans say it this way
K-drama confrontation classic. 자식 (lit. offspring, used as insult = punk/bastard) vs 사람 (person). Adding ~아 makes it a direct address. This is rude but appears in almost every K-drama. Severity depends on tone — can be playful between close friends.
From: K-Drama Common