I really do believe that babies are born into this world with a predisposed character type. Yes, the environment also plays a part into his or her character formation but genetics/nature and, god forbid, his soul from the past life re-imerges into your newborn's attitude.
Take for instance my son - for the first 2 weeks he was a textbook baby. He would just eat & sleep. Yes, he would cry but only because he was hungry and when I met that demand, he would snooze instantly. Then came the 3rd week of his life when he started getting gassy and fussy and would cry and even shriek as if in pain. When I looked it up in my baby books, they say that this is the time wherein they 'wake up' and head towards the adaptive stage of crying, fussing, etc ... from overstimultaion, to overfeeding, to over-everything. It seems as if they are on shock-mode from the adjustment of womb to life outside the womb.
I know all babies are different. My friend's baby never really cried as loud as mine or screamed immediately after waking from a nap (believe me, mine does all the time even in his dreams!). This made me do some researching (what's new :P) and looky at what I found here
So, what's your baby type? I think I have a cross between an active&fussy baby and yes, a colicky one too... I don't mind at all. I love him no matter what. My Santi was born into this world knowing what he wants in life. He demands his milk, attention and my love. That's my boy!