Notes: This takes place at some point after Luffy becomes the Pirate King. I'm assuming that Sabo is actually still alive and hanging out with Dragon because that's the sort of stuff Oda likes to do because he's a Christmas monster. Garp is enjoying his retirement on his son's expense.
Nami gritted her teeth and squeezed the hand in her own tightly.
Far out on the deck where the battle was raging, Chopper, Nami, and Robin could hear Luffy howl in pain.
"Nami, you're squeezing my hand too hard!"
"Good!" Nami shouted, wrapping Luffy's wrist around a pole as he tried to pull his hand out of hers. "Hurry up and get rid of those guys already! They're rocking the damn boat while I'm trying to have a baby!"
"Hold on just a moment, Nami-swan! I'll get rid of these bastards for you!" Sanji shouted in a high sing-song voice. They heard increased shouting from the invading Marines and a crackling noise that probably meant that Sanji had set his leg on fire. Then they heard an angry shout from Zoro.
"Stupid cook, you set my coat on fire!"
"Maybe if you weren't so slow, you wouldn't be having this problem! Our beautiful, wonderful Queen is having a baby and she needs me to be her champion!"
"What, her champion of bullshit?"
They heard an inarticulate gurgle of rage and then the familiar sound of expensive leather hitting steel began to overwhelm the rest of the noises.
"If you don't stop fighting each other, I'll kill you!" Nami yelled and then moaned in pain. "Chopper, get this thing out of me before those idiots sink us."
"It's almost out, Nami, just a little bit more," Chopper said, his voice steady and comforting.
"Never again," Nami panted. "I don't care if Luffy is the Pirate King, this is the only kid he's getting."
"You're doing very well." Robin smiled a bit distractedly as she wiped Nami's forehead with one hand and slapped a group of Marines across the face with thirty others. Outside they could hear Franky and Brook singing a preemptive song to welcome their newest crewmember.
"Hey, there's another ship coming!" Usopp yelled to the rest of the crew from his position on top of the crow's nest. "Shit, I think that it's Dragon's ship!"
"Oh, Sabo must have gotten my letter." Robin seemed particularly pleased.
Nami contemplated how much more complicated and loud things were going to get when Luffy's dad, grandfather, and brother all showed up. She threw her head back and pushed.
Out on the deck Luffy was flinging Marines bodily towards his grandfather on Dragon's ship while Zoro and Sanji continued to ignore the larger battle happening in order to fight each other. Franky and Brook had decided to take a refreshments break as they discussed what the next line of their epic song should be. Usopp had taken to setting the Marine ships on fire as Robin gathered up the men that Luffy didn't have a hold of and tossed them gently into the ocean.
However everybody stopped what they were doing immediately when they heard the sound of a baby crying inside of the women's cabin. Luffy dropped the man he was preparing to throw and let his stretched-out arm snap him quickly into the room. The rest of the crew hurried over to the door and peered excitedly in.
Nami was holding the crying baby close. She smiled up at Luffy as he approached her bed, his hand on his hat and his eyes wide.
"It's a boy," Chopper told the crew, springing back into his smaller form and collapsing into Robin's lap in exhaustion.
"A Prince." Sanji grinned around his unlit cigarette and for once Zoro didn't even feel like mocking his idiotic tone. Behind them Franky was sobbing in sheer and utter joy, leaning heavily on a grinning Brook.
"Here." Nami gently handed the baby over to Luffy. "You have to be really careful, Luffy. Babies are fragile."
And then she trailed off because the baby had stopped crying and even though she knew it wasn't possible, she could swear that the baby was staring back at Luffy with the same strange intensity.
"Hey," Luffy said. "I'm the King of the Pirates. You're going to join my crew!"
The baby gurgled and Luffy laughed delightedly.
Then Luffy's grandfather threw himself onto the ship and all hell broke loose. All in all It was a standard first day for a Straw Hat.