At four months Sam's entering the big baby race:
Weight: 17 lbs. 9 oz. (that means he's gained 10 lbs. 1 oz. since he was born) - 90th percentile
Length: 26 in. - 85th percentile
Head circumference: 41.5 cm - 50th percentile
So his head size is holding steady, but his weight and height shot up in the percentages. He's wearing 6-9 month clothing and is threatening to grow out of it soon. But we're used to big, fast growing babies in our family.
I mentioned how Sam discovered his hands and now he's discovering that they can be used for more than just sucking. Babies this age are like drunk people. When he sees something he likes he grins, drools and makes a grunting noise. Then he bats and grabs at the thing, usually missing it and possibly falling forward. At least he's a happy drunk. As long as he's not tired and he's been fed he's very agreeable. He's much more aware of people and his surroundings, but he doesn't have preferences yet. So Sam recognizes me, but I can hand him off to someone else and he's just as happy.
His sleeping continues to be good. He doesn't sleep through the night every night, but we're at about half and half. I'm not nearly as zombie-like as I was when Ben was this age, but zombie-ness does have its advantages. Zombies just stagger through life, not worrying about anything, and when I was utterly sleep deprived that's how I was. However, when I get almost-but-not-quite-enough sleep I get really grumpy. So I've just been unpleasant for the last four months. Ask Heath, I'm sure he'll back me up on that.