I was bathing Peter and Yaya wanted to stand aside and watch. Peter began to pat the water as usual, splash, splash, he always entertains himself in doing so. I didn't even notice when did Yaya began to say"beep, beep". Somehow, they formed a rythum, Peter will splash twice and Yaya followed by two beeps. Then both of them began to giggle, more accurately, laugh loudly. I was so amazed that even little Peter seemed to understand what they were doing and they did this over and over again for almost 5 minutes. I just sat there, watching these two having fun together, little Peter's body shaking up and down along with his loud laugh. I was very much moved by their joy and hated to take Peter out of the tub, though it was getting cold.