Soulmate au; Luffy doesn’t have a soulmate, he is a free & wild soul that cannot be bound to such thing. For him, his crew is all he need.
Or Soulmate au, but it’s his devil fruit who removed the soulmark/bond(s) he had.
It’s bring your grandson to work day! And now Luffy know some of the marines before even going out to be a pirate.
Just like Gol d Roger, Luffy has an illness & that’s why he doesn’t fear death. (His crew doesn’t know because it isn’t noticeable)
After having recovered from Magellan’s (did I write that name right?) poison, Luffy’s left with white hair.
After the war at marineford; to help Luffy stay down low, Ivankov change Luffy’s gender. Just for a little while. Maybe they came with Sanji at sabaody so they can go change back Luffy to his normal gender.
Luffy deciding to be a girl. (Either trans or like, for a mission, since I personally think he could theoretically change his own body physics with his rubber power, tho, maybe temporarily.) Maybe it happens while he’s at Amazon lily?
Have a funny one; Luffy asking Ivankov to change him into a girl so he can get the same treats as Nami & Robin get from sanji.
Luffy was doing great sneaking around Impel down before running into Buggy. Buggy was the one making the guards go on alert in the first place, so what if Luffy managed to sneak around them? Buggy is a great distraction already. (Which would also mean that he get to keep that map he had given to buggy in canon)
The straw hat pirates getting experimented on.
A pirate crew that has 3 captains, the 3 hat’s pirates or asl pirates. They exclusively talk in American Sign Language just to mess with people (+ it would be ironic & funny). [obviously they can also normally talk aloud]
Luffy being in a constant state of starvation because of his metabolism & devil fruit.
The first time they met Kuzan, the frozen arm of Luffy broke instead of getting the chance to melt it. Now Luffy is missing one arm.
What if in sabaody, Kuma never get the chance of sending Luffy away, nor does Luffy get an explanation to what happened to his crew. So now he’s assuming that they died + later his brother die (does he manage to get to impel down & marineford somehow or does he see his death on one of the screen?). So if there’s a moment that Jinbe or someone try to remind him of what he has left, he would believe there’s no one left. What would he do? Would he still go on with Rayleigh to train & get stronger anyway? Would he end it all? Would Jinbe or someone else manage to save him from himself?
Luffy using the nickname Shanks gave him instead of his real name (so his poster would say Anchor instead).
Ace going by Monkey D Ace instead of his parents name. How would that change the story?
What if none of his enemies life were spared?
When Luffy stabbed under his own eye, he actually made himself half blind or has some kind of problem with said eye.
Another I personally find quite funny: What if Luffy ask people if they poop because he himself cannot poop?
Luffy having a tattoo similar to Ace but it’s A S L U F F Y
Luffy gum gum balloon move but when he use it to protect others from a fall he act like one of those air mattresses that firefighters use; by slowly releasing the air he inhaled & thus not making them bounce off.
Nobody died at Marineford au (a scene after marineford); Luffy, curious, ask Whitebeard what exactly is a father. Did anyone ever really truly explained to him what are parents?
Luffy doesn’t seem to know much about love without violence. The majority of his family show their love with violence. Only Makino & maybe Shanks showed him a little, but it wouldn’t affect much of his way of thinking when the majority he see is Garp, and then after, the bandits & Ace (the same thought process could probably be said about Ace too). Kids observe & learn from what they see & how people act, so it would be quite easy for him to associate violence=love, which might also be why he say that being lonely hurt more than being hurt itself. Luffy & Ace clearly didn’t get much of an education (I bet Ace learned more about it with the whitebeards tho).
The flame flame fruit could have different type of gases as different flame flame fruits, kind of like the Zoan devil fruits has (like the 2 sisters of Boa’s having the same fruit but different species for example). So if both Ace & Sabo are alive they could still potential have the same fruit, just not of the same gases. Different gases can make different flames colours & effects.
An au where Sabo stayed with Ace & Luffy; Ace & Sabo somehow eating the flame flame fruit at the exact same time thus making them both be users of the fruit. Also they are now connected by the devil fruit they ate. Fire twins.
What Dragon didn’t only took Sabo, but also found Ace & Luffy being in danger at grey terminal, so he took them all in, realizing that Dawn wasn’t safe for his son.
One day, a devil fruit grew out of Nami’s tangerines.
Luffy never shouted out loud or told anyone that his goal was to be king of the pirates. But his crew knew it anyway. They are the one who say it instead. Maybe that could be a mute Luffy story idea?
Luffy telling Sabo he saw Ace at Wano (because he died for a moment).
What if both of Luffy’s brothers are truly gone & so luffy or Bartelomeo (did I write that right?) was the one finishing the competition in Dressrossa (obviously, if bartelomeo, he’ll be giving the fruit later to Luffy). What would Luffy do with it? What if he ate it (accidentally or not)? Since fire is an aspect of the sun, would it just technically fuel more his first devil fruit? Or would the rumours of eating more than one making explode be the truth? Would he truly explode or the affect of his precedent fruit protect him by stretching?
Since Luffy’s power are a little cartoonish, if he stretch/inflate his ears, could he possibly hear better & further away (actually, I think he might have already done that, be I’m not sure)? Also cartoon behaviour could also say that Luffy could have just gobbled up the big golden ball that was keeping his arm stuck thus freeing himself. At least, depending on the cartoon… still, it’s something funny to think about.
Luffy being related to the Shandians (did I write that right?) & having tiny wings that are unnoticeable under his shirt.
What if Luffy was a mink or a fishmen (or half. Oh or what about a toncatta?), but because he ate a human human fruit he now look human? Being a living being close in physical aspects to humans compared to Chopper, make him look exactly like a human, even tho he is not.
Kuina & Lami being somehow alive & working for the revolutionaries.
… I’ll make a part2… it’s getting pretty long.
