Robert Sheehan is basically just a giant ball of charisma, and it's an unfortunate truth that people like him don't stay in one place for too long. No matter how good Misfits was, especially during the first couple seasons, it wasn't enough to keep him there long term. His performance as Nathan, an utter knob that we grew to like almost against our better judgment, won him rave reviews from pretty much everyone. He had a magnetic screen presence that was hard to resist, and we knew he was going to be a big star someday. We just wished that we could have gotten another season or two out of him as Nathan. But alas, it was not to be. After the Christmas special at the end of the second season, Nathan and his lovably daft paramour Marnie headed off to Vegas, and that was the end of that. His departure led a mass exodus from the show, with the rest of the original cast leaving only a season or two behind Sheehan, doomed to be replaced by slightly lower quality versions of themselves. Robert Sheehan may not have found a role with as big of an impact as Nathan, but he's been working on progressively larger projects, and who knows what the future will hold?