Probably the ego from the guy who took what--no more than 15 minutes worth of screen time on TOS (even less on TAS), and elevated that to Sulu deserving not only his own ship, but a TV series. Nothing touches that level of delusional self-importance.
Oh, don't get me started on that man's obsession with self-publicity. For a bit player who did little more than say "Aye, air!", Takei is a seriously entitled media whore.
He should take a leaf out of Leonard Nimoy's book and learn some humility. And Nimoy was uh.... one of the actual stars!