Because he's got nothing else going on in his life right now, Sirius Black is ON TIME to this just to make sure that the awkward & uncomfortable is cranked up to eleven by the time everyone else arrives. He's not talkative, he's not excited to see most of you (like, he threw up twice before showing up), and he's more then happy to sit all by himself and listen to James' speech and be utterly unhelpful unless directly questioned.