For a moment the expression he gave her was terribly serious, but then the corners of his lips quirked into a smirk as she caught his puns. Sherlock probably wouldn't have even reacted or cred, nor would the people he worked with. John was a fan of puns however. His sense of humor wasn't very obvious to most, but it was there subtly if one looked hard enough. It tended to be more on the dry and sarcastic side.
"It's perfect." He commented as he put it on to try it out. It fit him quite well. She even knew what size to pick up and he barely knew anything about her. He felt a little bad. He'd spent so much time trying to avoid her and unsure how to react to her, he was aware now he'd missed out. He hoped she was't too turned off. The present was a good indicator that she didn't despise him for it at least. He hoped. He was rather bad at reading signals.
"It counts." He couldn't help but be amused at the gesture. "I'll have to thank her too." He was bad with children, but he'd been getting a little better between Bo and Ava. A little less stiff with them.