What role do zodiac signs, the Chinese zodiac, and blood types play in Korean culture?

These come up more than you might expect, usually in a fun, social way. The Chinese zodiac (띠), your animal sign based on birth year, is widely known, and people often work out your age politely by asking which animal year you were born in, since each animal repeats every twelve years. You will hear a lot of talk about the year's animal around Lunar New Year, and some people loosely tie personality traits to each sign. Western star signs are popular too, especially among younger people and in casual dating chat.

The really distinctive one is blood type personality theory, which is big here. Many people believe your ABO blood type hints at your personality, so being asked your blood type in a getting-to-know-you conversation is normal and not a medical question. The rough stereotypes are that type A is careful and detail-oriented, type B is free-spirited and a bit self-centered (this one gets teased the most, especially about 'B-type men'), type O is sociable and a natural leader, and type AB is rare and seen as quirky or genius-like. Almost nobody treats this as hard science; it is mostly a lighthearted icebreaker, like horoscopes elsewhere. If someone asks your blood type or your zodiac animal, they are just making friendly conversation, so it is fine to play along even if you do not buy into it.