Japanese Blood Types and Personality
Every Japanese celebrity writeup and every anime character description with any claim to authority gives the person's (or character's) blood type. Why? Because, thanks to a remarkable bit of Science! by a gentleman named Furukawa Takeji, the Japanese believe that a person's blood type affects their personality.
Each blood type has a personality profile. These profiles—which I took from a site whose location is long since lost in the mists of time, my apologies—are:
Type A
People with blood type A have a deep-rooted strength that helps them stay calm in a crisis when everyone else is panicking. However, they tend to avoid confrontation, and feel very uncomfortable around people. A types are shy and sometimes withdrawn. They seek harmony and are very polite, but all the same feel that they never really fit in with others. A types are very responsible. If there is a job to be done, they prefer to take care of it themselves. These people crave success and are perfectionists. They are also very creative, and the most artistic of all the blood types, most likely because of their sensitivity.
People with blood type A are also likely to be considered classic "type A's": stressed and conscientious. In anime, people like Hotohori are type A's.
The Third Hokage, Haruno Sakura, Hotohori, Heero Yui, Keiko (Kayko) Yukimura
Type B
People with blood type B are the most practical of the blood groups. They are specialists in what they do. When they start a project, they spend extra time understanding and trying to follow directions than others might. When they are doing something, all of their attention is focused on it. They tend to stick to a goal and follow it through to the end, even if it seems impossible. They tend to be less than cooperative, as they like to follow their own rules and their own ideas. They are individualists. B type people pay attention to their thoughts a little more than their feelings, and therefore can sometimes seem cold and serious.
People with blood type B are often considered more relaxed, freewheeling, and unconventional than other types, although not necessarily to an unacceptable degree. In anime, the genki, off-the-wall types are type B, along with any kind of well-intended character who's ruled by their impulses.
Naruto, Duo Maxwell, Miaka, Nuriko, Tasuki, Sagara Sanosuke
Type O
People with blood type O people are outgoing, energetic and social. They are the most flexible of the blood types. They easily start up projects but often have trouble following through because they give up easily. They are flighty and not too dependable. O types always say what's on their mind. They value the opinion of others and like to be the center of attention. Also, people with O blood are extremely self-confident.
Type O, the most "average" blood type, is considered the best type in Japan.
Quatre, Sailor Moon, Saito Hajime, Kamiya Kaoru, Tamahome