Dexter Morgan is an unstoppable killing machine. And what better way to fight an unstoppable killing machine than with America's favorite insatiable law-and-order cyborg? No, not Vincent D'Onofrio.Peter Weller, the star of the classic 80's sci-fi film Robocop has joined the cast of "Dexter: Season 5." According to Dread Central, he will appear in eight episodes, and will play a "troubled" Miami Metro police officer, as if there's any other kind.While there's no mention of the character of Robocop, I'd be surprised if they didn't use him in some capacity. The show never came right out and said that John Lithgow was supposed to be the character of Dr. Dick Solomon from "3rd Rock from the Sun." But once he dropped the C-Bomb at Thanksgiving dinner, everyone knew it was him.