From the "Ask Ausiello" column at TV Guide Online:
"Eric Dane — that's Jason Dean to all you 'Charmed' fans — has landed the pivotal role of Dr. Mark Sloan on 'Grey's Anatomy'. Mark is the creep who slept with Addison behind Derek's back. "
A few months back, I posited a theory that Dr. Greg House could have been the son of Dr. Mark Sloan of 'Diagnosis Murder'. (The fact that R. Lee Ermey eventually played the role wasn't a deterrent; House's mom could have slept around!)
I don't know how much we'll learn about this new Dr. Mark Sloan on 'Grey's Anatomy'; whether or not we'll learn of his parentage, background, etc. But I'm of the opinion that we shouldn't get worked up over him being the illegitimate son of Dick Van Dyke's character. I just don't see that as happening.
However, he could be a namesake. We know Dr. Sloan had a lot of relatives in the Sloan family tree (granted, a lot of them were bumped off in one episode). Surely one of them might have honored Mark Sloan with a child named after him, a cousin for Steve Sloan . And upon growing up, perhaps this new Mark Sloan decided to become a doctor as well.
But it doesn't sound as if he was quite as honorable as his predecessor.....
We shall see what we shall see.