How to say this in Korean?
I usually say " look who's here " so I'm wondering what it would be in Korean!!

Question

Answer

"Look who's here!" 
=> (어머) 이게 누구야! (female) / (어/야) 이게 누구야! (male) - in casual speech.
=> (어머) 이게 누구세요! / (어) 이게 누구세요! - in polite speech.

이게 누구야 is literally "Who's this!" but conveys the sense of "Who's this! (What a surprise!)" or "Look who's here".
It's usually said with a distinctive intonation expressing a surprise.

Don’t miss out on the opportunity to learn a language from the comfort of your own home. Browse our selection of experienced language tutors and enroll in your first lesson now!