Because we all know Zoro's a big softie to Luffy. Set after Franky joins the crew. Not slash, so those who take the first sentence the wrong way, get your minds out of the gutter! :)
The two aren't necessarily loud. More that Franky wasn't sleeping in the first place. Hours has passed since the glorious moment he'd boarded on this ship and promised not goodbye but till next time to his home. Yet the pounding in his heart, the short and powerful thrills that send shivers up his spine still has yet to pass.
So when Luffy crawls out of bed and slides to his first mate's, Franky notices. And for more than a second, he freezes, his mind going through every single possibility that he hadn't had in mind when he made Thousand Sunny but now realizes he should have had. He's met his fair share of people and had long ago learned that you could never tell by looking. Still, Franky worries with horror, why didn't anybody else tell him? Do they not trust him enough? Do they think he would judge them? Do they honestly think that he'd be bothered by the little aspects like that after all they've been through together?
Franky peels one eye open and watches Luffy sharply poke his swordsman in the waist and Franky has yet to know that if it had been anybody else, Zoro would be up with his katana in hand and blade at the poker's neck. Instead the swordsman grumbles as he swats away his captain's finger.
Of course, that just gives Luffy no choice but to poke harder.
"What?" Franky notes with amusement that Zoro doesn't even sound surprised, just very very irritated. The green headed pirate scratches his head as he blinks up at his captain. "What this time Luffy?"
"I'm hungry," Luffy whispers with a grin.
Franky has no idea what that has to do with anything but apparently the swordsman does because the older teen groans as he drapes an arm over his eyes.
"No."
"Please?"
"No means no Luffy."
"Zo-ro." Luffy tugs his first mate's shirt as he whines. "Please?"
And Franky watches the swordsman, the man who didn't even flinch when his captain declared war against the whole world, the man who didn't back down against any threat, any enemy, anything, take one look at his captain and quietly groan. Franky realizes with amusement, that that same man, Pirate Hunter Roronora Zoro is going to fold.
"Zoro, help me raid the kitchen?"
The ex-bounty hunter makes a muffled sound from under his arm that sounds suspiciously like damn puppy eyes when Luffy tugs his friend's shirt harder.
"Zo-ro."
"We'll see," Zoro answers in a tone that really means yes, I'll help you raid the kitchen.
The two sneak out while throwing wary looks at a particular snoring cook and Franky chuckles to himself.
This was family. Nothing else.