Zack is very much akin to an overstimulated dog, and if he wasn't sitting down, he'd be relentlessly going in circles he's so wound up. But Cloud's request has him pausing suddenly, and then apologizing with a sheepish look.

"Sorry, I got a little excited." The color on his cheeks has deepened, leaving a brush of red over his cheeks, and that lopsided smile. "You're just really cute, y'know? But I can behave, promise. What do you want me to do to you, Cloud?"