The Doctor took great amusement in displaying his Time Lordy traits to his human friends. The two hearts, regeneration, even his respiratory bypass system, even if it hadn't been needed yet, as of late. One trait, however, was more inconvenient than it should be. The Doctor's bladder could hold quite a bit more than a human bladder. About 2.5 times as much, but that was all he needed to mock Mickey at every opportunity. He did see the hypocrisy in that. Because, while it meant he only needed to pee every 2-3 days, depending on his liquid intake, it made it quite difficult to keep track of how long it had been since last time, when he was adventuring through time and space, even getting imprisoned several times. Honestly, it's a miracle he hadn't had an accident yet. At least not in a couple of regenerations...