With him, I ran up and down the street holding onto his shirt as he careened on a balance bike, a contraption that wasn't around when my own children were young.
With him, I ate pretend hamburgers on plastic buns with plastic tomatoes. Unfortunately, he did eat some very real play dough while I wasn't looking.
He "checked my ears" with the jack end of a baby monitor, "talked on the phone" with our portable, and covered me with his baby blanket. With his giggles and grins he reminded me of what I've been missing since my own kids grew up.