Mary & Clay
It was very doubtful that Mary was going to call him Clay, at least at this point in knowing him. Mary called everyone by their title until they were close enough to her to no longer warrant it.
She glanced at him when he commented on his body heat. "Really? Warm enough to give off heat? That seems odd. I believe Mr. Rogers has something similar as well."
Steve's was due to that serum he had been given, Mary knew that much.