[Bucky could have done without the whole new outfit change, and frankly, the thought of having a dance while those creatures still lurked outside was less than appealing to him. So he stands watch near the doors, walking around the entire ballroom a few times to make sure there's no threat to anyone, before returning back to his "post" of sorts.
That's where Korra catches him, with her question, and he turns to her with a surprised look that then melts into a small smile.]
You feelin' it, too? [He's been fighting against the urge to dance all night too, only kept here by his force of will and the thought of what could happen to everyone if no one was guarding the place.]