Isaac's First Catchphrase

We all have them--things we say that really have no meaning on their own and gain meaning after we say them a bunch.  Thing of them as personal catchphrases.  Well, Isaac has his first--Num, Num, Num.  We used to believe that it had to do with him liking the food he was eating, but we have caught him, while playing quietly on his own, saying this phrase to himself.  It caught on and now we have all kinds of variants.  See this video: