Ernie Hudson has been cast as King Poseidon in ABC’s Once Upon A Time. He will appear in episode 15 of the fairytale drama’s current fourth season. In a twist, in addition to being the the powerful deity of legend, in the OUAT world, we will also discover that Poseidon is the father of the villainous Ursula, played by Merrin Dungey. The two will be joined by JoAnna Garcia Swisher, who will be reprising her role as Ariel. Hudson is repped by Artists International Management, LLC.