When it comes to parties, James Potter is a kind of mythical being, because somehow he manages to be and do everything.
It’s not enough that he co-organises basically every party Gryffindor house ever has: he and Sirius appoint themselves joint heads of the Gryffindor Party Council somewhere around third year, which is fine with the older students because those pesky little kids know how to obtain everything necessary for a good bash and will always take the blame if McGonagall comes storming in.
No, James can’t just sit back and be at a party. He’s the bloke who dances with anyone and everyone and even himself when everybody else is worn out. He’s the bloke who will gladly take you up on that ubiquitous challenge, I bet you can’t down this in one - he’ll drink you under the table, and then Conjure you a glass of water while you splutter, regretting your choices. Then he’s off, to talk to somebody or tell some crazy anecdote that can’t really have happened, can it - oh, wait, it’s James Potter, of course it can.
He can also be found on the sidelines, sitting with those who like to observe, making them feel comfortable with the fact that they’re not in the thick of things, because although for a long time he’s a dick and you never know when you might find yourself sprouting a tail or something similar, if James Potter’s talking to you then you’re automatically popular, at least for a moment or two.
And then next morning, when everyone’s grey-faced and flinching at sunlight, he’s fresh as a daisy, laughing with his friends like he was in bed by nine, and everybody groans and curses James Potter, because damn it, is there anything he can’t do?