"Just for one night," Tony had said.
"It will be fun," he said.
One thing Bruce had trouble explaining to people – or, maybe, they just had trouble understanding – was that whenever there was fun around, the Other Guy wanted to join in.
He wandered quietly through the halls of the S.H.I.E.L.D. base, taking his time to observe the adamantium that lined the walls and pretending to be interested in that. Other hallway commuters, mainly S.H.I.E.L.D. agents he vaguely knew, instinctively moved as far away from him as possible when passing by, but he didn't even glance anymore; the dull pain of loneliness that the Other Guy's involvement brought barely hurt him anymore. And the Other Guy didn't seem to mind at all when people ignored them; it was only during an upfront attack that the monster wanted to be let loose.
Bruce had told everyone that he had tamed the beast to a controllable extent. In reality, the Other Guy was like the common cold; you can do your best to prevent it from appearing, but when it does appear, there's no cure, just some diligent treatment until it is subdued.
All Bruce had done in the past decade was perfect his hygiene, in a way, so that his other side was less likely to show up when not called for. But he wasn't a complete germaphobe and he knew he never would be; he could never explain this to anyone else, that he was sure of, but in a way, the Other Guy's pain brought him comfort. It was one of the few things they both shared besides a body.