My first thing that impressed me with ds was the lack of sleep starting around 3 months. And his eyes. He just had these huge saucer eyes which never closed (hardly ever, anyway).
Every baby picture we have is of him completely lazer-beaming everything...a crafty friend of ours took some rolls of film just of ds and she ended up making a t-shirt for Dh that was all the pictures pretty small like on a proof sheet - they were stacked 3 frames tall and each one was about 1" wide across Dh' chest. Basically it was just like white rectangles with eyes and more eyes. He was intense, still is.

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