I'm not sure, but Mudpuppy may have said his first word this morning as we were leaving the prayer vigil at the Veteran's memorial this morning. "Let's say goodbye!" I prompted. And he raised his hand and waved a little bit (he still doesn't quite get it) while saying something sounding very close to "bye bye." We'll see whether he repeats it. Up until now, he's imitated ("ba ba ba," "da, da, da") but without attaching the sound to anything concrete.
We will wait and see.