BUBBLE!!
It was first expressed in the bath tub, and later repeated for dish soap bubbles. We were trying to get it on video, showing him bubbles and saying the requisite "Bubble. Bubble! You can say it. BUBBLE!!" Of course He declined to satisfy our requests.
However, when I replayed the video for him to see himself, he looked up at us and quietly whispered...
"bub-buh"
(sigh......and melt......)
