Michael Rooker had this to say over his Twitter account, "on my way to Atlanta soon to work with my new best friend Frank Darabont on 'The Walking Dead'"
Some more stellar casting in this series shows why it just keeps getting better and better. Question is, though, "Who the hell is Merle?".
He's not a character in the series from what I can recall, unless he was very minor. Here's some early characters who have yet to be cast that he could kind of fill the shoes of.
Maybe Merle is a combo of two of them or maybe he's the first to be cast in a brand new original role just for the series. Rooker might best be known as portraying the famous serial killer Henry Lee Lucas in "Henry: Portrait of a Serial Killer", but he was most recently in 'Jumper' playing Anakin Skywalker's father. The guy's awesome whoever he's playing.