Assuming you haven't seen the show he is VERY good at playing the part. Like he is absolutely hilarious. He is definitely the primary reason for the shows success.
Her role on the show was virtually meaningless. I didn't even recognize her until my wife pointed her out. Why would they want to bring her back? Makes me think the show is not doing well in the ratings.
It's a show that grows on you over time in my opinion.
Here's what happened to me...I watched the whole first season on DVD in a couple days and loved it. The more I watched the better it got because you get attached to the characters. Then I watched the second season on TV and still thought it was very funny. However ever since then it still has it's moments but overall it seems like they keep trying to just stretch things out. The plot isn't going anywhere it's just them doing funny stupid stuff (which is great for a couple seasons but you can only do that for so long). The good moments it still has make it worth still watching for me but I just wish I could still view it as I did the first several times. I think part of the problem is that I was still getting acquainted with the characters in the first two seasons but by now like I feel like I know all their little quirks and stuff so I'm ready for something to actually happen.