I had twin boys. Right from the start one of them was very content to lie in his bassinet in the living room and just look around. He also preferred sweet foods as a baby. His brother, who weigh 2 lbs. more at birth, wanted to be held more and was always hungry. He was the squeaky wheel that got the oil. These difference seemed to continue even today. The one who wanted to be held more has always been very cuddly and a huggy bear, even at 11.5yo. He's also an adventurous eater who loves to try new foods. He really gets into eating and thoroughly enjoys a good dinner. (Sometimes you can even hear him talking to himself..."mmm, this is really good.") The contented one has always been pretty easy-going. He says he's the peacemaker among friends. He has a quick sense of humor since he was a toddler and he can be quite dry. He's a keen observer of human behavior...then he turns it into a joke. He's been an okay eater but would rather have junk food than a real meal. He's also been the one who has needed more sleep. He gave up naps later, is the one who falls asleep first in the car, wakes up last, goes to bed earlier, etc.
My daughter, who is 18 months older, came out with her eyes wide open and looking around. The doctors and nurses all commented on her bright eyes. Even when she was a few months old, people who still comment on her bright eyes and how alert and aware she was. I can't remember much else but she is very aware of her environment and is sensitive to when she thinks people don't like her or have an attitude to her. She's hypersensitive about it, I'd say.