The Good Wife has to be probably my favourite show on TV. Every episode is awesome and they get some awesome actors to play even minor roles.
One of the major story lines in the fourth season sees the return of Kalinda's ex husband, and as far as I'm aware at the end of Season 3 the part hadn't been cast even though it was heavily foreshadowed. People thought they might stunt cast it with a big name, but it turns out they've cast Marc Warren, whom Who fans will know from the less than stellar episode "Love and Monsters".
He's definitely playing a very different character in this to what he played in Who! Even if you aren't a Good Wife fan, try and check it out.
The same episode also features Nathan Lane.
I keep myself very spoiler free for the Good Wife, I remember when I watched the first episode that featured Michael J Fox I had no idea he was going to be in it. His very first appearance was just in the background and I remember thinking "god I love this show". It was great seeing him on TV again.