It's inevitable. In every class I've ever taken that had more than 10 people, there's always been that one person.
You know who I'm talking about, they're the ones who ask the same question that was asked five minutes ago, or who feel the need to comment on every single topic even when they don't have anything to add, or who nitpick about stupid little things on the syllabus, or who argue over the right answer to a test question for ten minutes.
They are always annoying, sometimes to the point of distraction, and they seem to be living on a different planet than the rest of the world where people are capable of paying attention and having relevant discussions on an issue. I don't know why it is that there's always one such person, but it's a truth that I've seen confirmed time and time again in my classes and my new grad school classes are no different. It's only the first week of class and I've already identified who they're going to be - now I just have to hope that I don't have to do any group work with either of them, because that might just be too much.