Laura did not know why the Deadpools were singing, or what they were singing for that matter. But she had learned already that there was often no obvious reason for anything Deadpool did. For someone who was still trying to understand the motivations even behind normal human behaviour, it was disconcerting until a certain point, beyond which she remembered that there was simply no point in trying to understand and relaxed. Deadpool was what Deadpool was. At present he was not a danger to her, at least.
She was glad the fight had finally begun, though. She didn't like sitting, waiting, knowing they were there but not quite in a position where she could attack. Her claws unsheathed she became a pointy thing of beauty, almost appearing to be performing a choreographed dance that just happened to involve a lot of bloodied Badoon, an increasing number of them dead or dying.