They’re having muscles around their mouth surgically cut into smiles.
According to The Atlantic, the "Smile Lipt" plastic surgery procedure is becoming increasingly popular in South Korea.
Facebook: aone-plastic-aesthetic-surgery
Aone Plastic & Aesthetic Surgery have apparently patented it, promising to enhance people with "short mouths" or "downturned mouth corners."
Via Facebook: AonePlasticSurgery
Smile Lipt (Lipt = Lip + Lift), i.e. mouth corner lift is Aone Plastic & Aesthetic Surgery's invented & patented method which physiologically lifts up mouth corners by adjusting muscle balance around the mouth corners. This method is different than the method introduced in the West, which only physically lifts up mouth corners.
Rocket News explains that surgery aims to reshape patients' mouths to look more like Korean entertainer Min-A Shin.
