In case if you never heard of it, Blood Type Cartoon originally came from Japan. In Japan, most people will see your characters from your blood type. Japanese think that for each blood type, people will have a particular character, because they believe that blood type determines a person's personality.
I just find the cartoon very funny. XD
Note: for you who is not familiar with Japanese/Korean humor, you might find the comic a bit odd or not funny at all.
Best traits: Earnest, creative, sensible, reserved, patient, responsible
Worst traits: Fastidious, overearnest, stubborn, tense, conservative
Sounds like a Melancholic to me.
Best traits: Wild, active, doer, creative, passionate, strong.
Worst traits: Selfish, irresponsible, unforgiving, unpredictable.
Sounds like a Sanguinist to me.
Best traits: Agreeable, sociable, optimistic.
Worst traits: Vain, rude, jealous, arrogant.
Sounds like a Choleric to me.
Best traits: Cool, controlled, rational, sociable, "split personality".
Worst traits: Critical, indecisive, forgetful, irresponsible.
The efficient way to study:
If the inner hearts of each blood type was a house: