Mark plays Jamie's brother Seth Martin and first appears in Episode #21 of Season One. He is also in episodes #22 and #24, and then joined the cast for Season Two. He is good friends with Stacey J. Aswad and was recommended by her to Dave Christiano. Mark's main episodes are the two entitled "Jamie's Brother" in Season One, and he also plays a key role in the first two episodes of Season Two. Mark appears in a total of 15 episodes.