Humor wasn't lost on Bucky, obviously, but it was rare enough that when he expressed it and received a laugh for it he did feel a bit of a euphoric rush. It made him feel human again and some days he was a little desperate to cling to that feeling. Getting a rise out of Barton was enough to make him feel a little better in general, and about everything going on around them. He'd take it. Quietly, admittedly, he also kind of liked hearing him laugh.
When presented with his own copy of that particular gem of a drawing, Bucky reluctantly took it and gave it a look over once again. Yeah, that shit was just weird. There was no way around that. Why anyone would think 'man, it'd be great to draw the Avengers as mer-people' was beyond his own comprehension but now he had this piece of 'art' and he definitely was going to keep it. "Wow, thanks," he said. "Not sure if I should hang it up right away or keep it tucked away until I want to look at it and have some pretend time." Thank God he wasn't on there. Bucky didn't think he'd be able to really handle seeing himself as a Merman.