Where is "appa"?

In high hopes of staying true to our roots (Sung and I are both Korean-born - Sung was raised in the US and I was raised in Japan and the Philippines) by making Korean the primary language in our home, Sung and I have been speaking to Collin only in Korean ever since he was born.

Collin's first official word (meaning, he knew exactly when to say the word) was "appa," which means "daddy" in Korean. Naturally, Sung was completely ecstatic when he first heard the little guy say it and has been grinning ear to ear ever since. Well, until a few days ago when we got this on video (OK, so we THOUGHT Collin knew exactly when to use the word - more practice, anyone?):



Um... If you don't get what the clip is about... Look closely where Collin's "appa" is (right next to him) when Collin is chasing after an unidentified moving person (clearly NOT his "appa")...