Only Phil Mickelson, right?
According to Golf Channel, Mickelson almost forgot to register for the 2013 PGA Championship. At PGA Tour tournaments, players have to register before the first round and Mickelson still hadn't done so as of Wednesday.
He didn't practice at Oak Hill on Wednesday (I have no idea where he was, he probably doesn't know where he was) but he strolled into the clubhouse at 1:30 in flip flops and a t-shirt when he finally remembered what he had to do.
Like I said, only Phil Mickelson.