To "Kak" someone is to hit them up on KakaoTalk. If you're apps crazy in this smartphone age, I'm sure you've heard of KakaoTalk. It's the Korean version of WhatsApp and allows you to follow your favorite celebrities who have accounts on the app. 2Yoon revealed their phone numbers which included 2407, to match their latest song "24/7." Fans can add their number and add them as Kakao friends. The reaction to this? Cube Entertainment said, “Every hour, we receive hundreds of phone calls, so we haven’t been able to actually reply. We hope fans will try messaging instead of calling in so the 2YOON members can actually read the messages and respond.” Have you added them? Who would you like to Kak?