Don't take this the wrong way, Tony, but you smell funny.

Hiding the arm wouldn't change that, it'd just leave him trying to figure out the source of that scent, and confused. As it is, there's a moment or two where he's pretty obviously thrown by the arm, glancing that direction before getting his eyes back on Tony's face.

"This is the place. Kind of makes me want to know who McAran was." He hadn't looked into it, but having Tony there reminded him. Stark Tower and all. "What happened with the arm?" What, is he supposed to use tact? With any Tony? Please.