D., does he have a reason to talk? What I mean is do you automatically just do things for him when he cries or fusses? I know my last son (of four) wouldn't talk forever. Then suddenly tadahhh..he wouldn't shut up. After reflecting on the issue, he didn't have to talk. He could just look at the refrigerator or the tv and someone would jump up and ask him what he wanted... or just assume he was thirsty or hungry and get it for him.
If you are just doing because your a loving mother, let him cry for a minute or fuss and see what happens. Be patient though, if he can say spongebob and fish..he can say other things also. You might check his hearing to make sure he understands also. Snap your fingers behind his ears when he isn't paying attention and see if he turns in the direction of the noise.
There are numerous reasons for not talking, but don't fret too bad, it sounds like he's pretty active.