A/N: Long ago the thought came to me that if Luffy can understand and communicate with more creatures than the base one piece human being, he's going to start empathising with some random cow he meets in a field.
Also, I'm flexitarian with some opinions on plant based (but not plant exclusive) diets so know that a.) for humor's sake it's called vegetarian but Luffy is def doing some diet splicing. And b.) hmu (and google) with diet questions and recipe recs.
(Shout out to my OP discord friends who I crowdsourced Luffy's animal friends from, no context given, thank youuu)
Vegetarianism and Other Threats to the Order of the Universe
"Look what I can do!"
"Hmm?" Luffy raised his head, looking out over the railing at the sudden call. Chopper, who he'd been chasing in a game of tag kept running and disappeared around the corner, unperturbed by the sudden voice.
This was hardly the first time such a thing had happened, ever since he'd started training with Rayleigh there was an increase in conversations that Luffy just… listened in on. The time he could hear Hancock and her sisters on their ship from across the island, the time Rayleigh had been on the snail phone while Luffy was out training for the day. More than that too, but he didn't know where they all came from, or why he heard certain things and not others.
On Rusukaina he'd blame it on his not fully trained observation haki, but now he knew he had full control over that, but he could still pick up the most random of conversations. He didn't even know where a lot of them came from. Who was out on the sea talking? Was he tuning into something on another ship? He couldn't see anything on the horizon…
Suddenly, a sea king breached, off to the port side. The creature, a snake-like eel with elephant ears, or maybe one of those cobra capes, leaped into the air, rolling onto its side in midair and crashing down with a splash. Luffy grinned, trotting over to the railing and leaning against it to watch as the creature submerged, only to rise up again. The Sunny rocked with the force of the waves being made so close but without much thought, he wrapped one wrist around the railing to secure his place, enjoying the show and listening to the almost distant cries of his nakama as the ship lilted this way and that.
"I see, I see." Another voice said and Luffy grinned as another, slightly larger sea king rose from the depths some distance from the smaller one. "Isn't it more fun to flounce around like this near the nest? Humans lurk on these waters, and not weak ones like we chased the other day."
"But the water here has currents, so it makes the splash bigger! Watch!"
The smaller one breached again and Luffy frowned. There was some kind of connection here, between the sea kings and the voices, but he wasn't quite sure…
"Luffy!" Nami's shriek ripped him from his thought. "What are you waiting for? Beat up the sea kings before they capsize us!"
"Huh?" He shouted back, one hand going to hold his hat in place as a particularly violent swell tipped the ship this way and that. "They're not gonna capsize us, they're just playing around!"
And they were, he realized. The voices he was hearing, the sea king splashing off to port, they were the same. Could sea kings talk? Apparently, but they must not very often because he couldn't usually hear them-
"I see a ship over there, we should be careful." The voice was much quieter now, as though their voices were getting further away and yet their shapes seemed just as close. Still, even as Luffy listened the voices continued growing quieter until they dropped into nothing, midsentence, and the sea kings still lingered in the seas where they were.
"Luffy, listen to Nami-san!" Sanji yelled. "If you catch one of them I'll cook it for dinner!"
"No, Sanji, they're too far out at sea for him to go after!"
"Take the marimo with you! Mossballs like water."
"What are you saying, swirls?"
Luffy continued to frown at the sea kings, thinking carefully about what Sanji had said, how many times he had said it, how many times he'd eaten sea king- which tasted delicious but…
"Hey, Sea Kings!" Luffy called, waving his arms over his head. "Do you all talk?"
"What's he going on about?"
"I don't know. It's Luffy, who ever knows."
The sea kings didn't respond, they didn't even look in his direction. He was probably too small and quiet. Still, he remembered all those times he heard things in the middle of the night and thought a ship was passing close. How many of those times was it sea kings? Why couldn't he hear them as well as the voices of other humans?
"Luffy, do you want dinner or not?"
"I want dinner!" He snapped his head up towards the second level deck, where Sanji was gripping the railing and glaring down at him.
"Then go catch one of those sea kings! I've got to get it marinating before noon."
"Nah, Sanji. I don't think I want to eat those sea kings." They seemed really close to one another, and they weren't bothering him…
"What? Why not? They're just like every other sea king!"
And that sealed it. He turned up and frowned at Sanji.
"I don't think I want to eat sea king anymore!"
Sanji gaped at him, from somewhere else on the ship there was a crash.
"B-But Sea King is one of your favorites!" Sanji murmured, and then grit his teeth around his cigarette. "Why not?"
"You tell me not to catch everything anyway!" Luffy accuses. "Some of them don't have good meat! (Even though all meat is good). And you always like preparing fish fish instead of sea king fish. And I usually fall in the water trying to catch them!"
"Since when has falling in the water bothered you?" Sanji yelled back.
"Since always! I can't swim you know!"
Sanji stares at him where Luffy stands sternly with his hands braced on his hips. The ship rolls underneath them but evens out as the sea kings dip deeper into the depths. His cook's face looks gaunt with fear and dread. He almost shakes as he forces the words out-
"L-luffy… are you… V. V. Vegetarian?"
Whispers rise from the other side of the deck where Usopp and Jinbe had tuned in and now debated fiercely what could have shifted the order of the universe in the last hour or so. Chopper is hiding (ineffectively) behind the corner of the ship cabin and looking at Luffy like he's an imposter.
"I don't know what that means but I don't want to eat anything that could be my friend!"
Sanji seems relieved but Robin chooses that moment to set down her book and sit up in the lawn chair. It comes across as just slightly threatening.
"That's an interesting way to phrase it, captain." she smiles. "Especially since you have always been so good at making friends."
"Yeah!" Luffy pumped his fist. "Friends are the best!"
"Well, since you're so good at making friends that eliminates quite a few options from your diet. " she begins counting them off on her fingers. "You just listed sea kings in that category, so that's an evolutionary branch. Chopper is a reindeer and you're friends with him so that eliminates reindeers. Would you count proper deer and moose as friend material?" Luffy shrugs. "We'll leave them on the menu for now. You made a friend in Dressrosa, didn't you? He was a Bull?"
"Yeah, Bullsy!" Luffy cheers.
"So that's beef. And Billy from Shiki's floating isles was a good companion, not to mention you were all rather close to Carue back in Alabasta, if I recall, so that's ducks off the list. Are there any other animals you've befriended over the years?"
"Ahh…" He thinks. "While we were training I made friends with a lion, a gorilla, and an alligator!"
"Oh my." Robin says placidly.
"Wait a second, Luffy." Sanji sputters to life. "Never eating beef again? Or duck? You can't be serious!"
"Don't forget whales." Brook chimes in from the crow's nest above, leaning out over the roof like a very strange weathervane. "Laboon would have my head if I didn't remind you! Or what's left of my head, yohoho!"
"You have a lot of animal friends, actually." Nami taps at her chin. "Remember in Alabasta those duongs beat up Usopp-"
"But you became their teacher." Robin blooms a hand beside her and counts out more fingers. "There was that crab to think about too! And Eyelashes the camel!"
"Eyelashes was no friend of ours!" Usopp shouts, rising to the offense. "He was a pervy camel! He only cared about you!"
"Sure but a friend of a friend, right?" Nami winks.
"No! Others take priority." Usopp crosses his arms and starts listing. Robin ticks off more fingers, Sanji withers a little more. "Don't forget! The wolves we partied with on the Sky Island! A pact was formed that day… and the octopus that carried us out of that hedgehog marine base? Surume! Another octopod we should remember in our hearts- and Megalo! Without him could we have pulled off the Fishman Island plan at all?"
"Ah, don't forget the Lapins!" Chopper squeaks. "They helped out a lot, and you helped them so you like them… don't you?"
"Sure!" Luffy nods.
"And um, the south bird was nice too." Chopper continues shyly. "And Zunisha could talk to you and Momo a little so…"
"That creepy cerberus dog from Thriller Bark!" Usopp bursts out. "That was a fox too right? And starfish! Can't go eating Pappagu's cousins!"
"If you're counting Cerebrus you might as well count the snake that ate you on the Sky Island too." Nami puts in sourly. Robin ticks it off.
"Ow, don't forget about all the water bulls that help out around Water 7!" Franky shouts from his workshop down below.
"Chouchou." Zoro grunts.
"If they take good care of their transponder snails people are known to form very close bonds with them." Jinbe says.
"Are you saying I can't even serve him escargot?" Sanji croaks.
The deck stills and everyone seems to consider once more what they're discussing.
"Well I wasn't really saying don't eat camels!" Nami laughs, high and squeaky. "I just! Got a little carried away!"
"Yeah you can eat foxes too!" Usopp says. "And, uh, duongs too, wolves-"
"No!" Luffy shouts and it strikes out like a gong. "I don't want to eat any of my friends! Or anybody that could be a friend!" He tugs at his ear and glances back at the sea he'd turned away from to face his crew. The seakings are long gone but his head still rings a little with their voices. "They're just having fun. And I'd rather have fun with them than eat them!" He nods, resolutely. "Sanji, only serve me friend free meals! But makes sure there's lots of meat too."
"H-How." Sanji asks, strangled. "You'll only eat… bears, fish, and… dinosaurs!"
("Do dinosaurs count as friends?" Usopp asks under his breath. "We hung out with them on Little Garden-" But Nami shushes him before he can go too far.)
"I don't know." Luffy laughs. "We eat a lot of fish anyway! And you're the best chef ever Sanji so I know you can do it!"
Sanji groans from where he's slumped against the upper railing.
"There are some very good meat alternatives nowadays." Robin says and passes a paper across the deck via several hands. "Here's a list of all the friends Luffy will no longer be consuming, Sanji. I'll see what I can do about obtaining a vegetarian cookbook for the library."
"What's vechetalian mean?" Luffy demands. "Sanji said it earlier too!"
"That one's simple, Captain." Robin smiles disarmingly and all her extra limbs poof away in a cloud of flower petals. "It's a friend free diet."
A/N: Usopp: You know I met some sentient plants during my two years train-
All of the straw hats: Not another word