I think he's an introvert because of his generally self-contained demeanor, in both scripted and unscripted situations.
I think NT because of this:
But I can't decide whether the self-parody is Ni or Ti... so for now, I think INTx.
I have no idea where the ISTP idea came from -- and to me, the idea that he's an NF is pretty literal from his scripts and his allusions to MLK jr (who was an ENFJ, right?), and not at all based on his demeanor.