Jonathan hams it up.
I always thought a baby's first word was a discrete event, a definitive moment. Parents remember the first word forever after, and it can even give hints about the developing personality. However, at this point it's safe to say that we don't have any idea what Jonathan's first word was, or even if he's actually said it yet.
We're doing a lot of double takes here these days. The nanny asked Jonathan if he'd wait downstairs while she went to change Cara, and Jonathan said "okay." Chris walked in the door this evening with his usual "Hi Jonathan!" and we both heard him reply "HiDad." If I leave him in the crib to go wash my hands, Jonathan will start wailing, but he wails "MMMMa MMMMMa MMMMMa" instead of his general-purpose holler. He still points out the "B----uh" at the bird feeder, but the nanny swore she heard him say "squirrel" one time. All of these might qualify as an actual word, but he doesn't do any of them reliably, and we're left looking at one another and saying "Did you just hear that?"
This morning I was kind of late to work, and was eating my Cheerios downstairs while Chris was in the shower. I heard an enormous THUD and instantly thought Jonathan had learned to climb out of his crib. So I sprinted up the stairs and opened the door to the nursery. Jonathan was safe and sound, but the light and the noise woke him up, which kind of obligated me to hold him until Chris was ready to take over.
Jonathan and I were sitting on our bed and he was rubbing his eyes, trying to wake up. Chris came out to get dressed and laughed at Jonathan. He asked him "Are you still sleepy?" expecting Jonathan to sign "sleep." Instead, Jonathan said "yeah." Then he deliberately leaned forward, rested his head on the mattress, and gave an exaggerated sigh.
I may not know what his first word was, but I'll always remember his first joke.