Walking in, as soon as he sees someone is there and completely naked, he turns around immediately and starts leaving as he spurts out, "Oh! Sorry! Didn't realize." A second or so later, what he just saw actually registers and he rushes back in, brow furrowed when his brain confirms what his eyes are seeing. "I'm gonna need some kind of explanation here."
His head is hanging down, the commando half asleep from being unable to do much more. So when he hears the door slide open, he raises his head and gives a half-smile at seeing who it is, only to be confused by Steve's sudden rush out. But when he came back, the smile was more of showing his nerves than anything else.
"...James played a prank."