"Suddenly appear" is "갑툭튀"(kap-tuk-twi) in Korean.
"Comes out suddenly” is called as 갑툭튀(Gaptuktui) in Korean. It is an abbreviation of 갑자기 툭 튀어 나오다 (Gapgagi Tuk Tuieo naoda).The literal meaning is Suddenly (갑자기 Gabjagi ), pop (툭 Tuk ), Apper(튀어나오다 Tuieo Naoda ). When unexpected event happens like in the Horror movie, the ghost appears suddenly, we use 갑툭튀(Gaptuktui).