"What is your blood type?"
"(Insert name of Korean Celeb here) is blood type (whatever)."
At times Koreans seem to be obsessed with blood types. If you look at fan sites for celebrities most will actually have the star's blood type listed. Every Korean knows their blood type.
My students were flabergasted when I told them I didn't know my blood type. When I told them most Canadians, at least the ones I know, don't know their blood type, they thought I was joking. So, I asked why they needed to know a person's blood type. The answer was because it tells you their personality.
Evidently there is a school of thought that says your personality is linked to your blood type. Blood type B can make a bad significant other according to the "study". Most Koreans I knew believe in personality based on blood type. Much like a lot of Westerners believe in horoscopes. I had one Middle School student who was obsessed with the group TVXQ. She knew the blood type of each member. That was kind of ... creepy.
When I looked up blood type personality I was a little surprised that Koreans put any credence in it. It was developed by the Japanese. Considering the level of hatred Koreans seem to have for the Japanese it seems strange that they would embrace the idea of personality by blood type.