Textbook vs Real
Textbook안녕히 주무세요, 연진 씨an-nyeong-hi ju-mu-se-yo yeon-jin ssi
Real잘 자, 연진아jal ja yeon-jin-a
Why Koreans say it this way
Deceptively warm. 잘 자 (sleep well, casual) vs 안녕히 주무세요 (sleep well, honorific). Adding ~아 after a name is intimate — using it with an enemy is deliberate psychological warfare. 주무세요 is the honorific form of 자다 (to sleep).
From: 더 글로리 EP12