Do you know what "wat" means?

So last night Dylan brings me his juice cup. As I reach for it I ask him if he wants juice. He grins, puts the cup behind his back (his favorite trick lately) and says "wat". So ask him again, do you want some juice? He shook his head and said no then he said "wat" again but in 2 syllables "wa at". Suddenly the light starts to flicker and I realize he is saying "where at"! So I said where is Dylan's cup and his eyes lit up like crazy and he said "is" (here it is)! He is so cool!