So what with Sanji having some childhood history and so forth, I wondered what it might be like if the rest of the crew got backstories out of nowhere that make no sense at all. Bear in mind that this is in no way serious and is the result of cider. So here goes.
Luffy So Dragon knocked up a rice cracker maker and Garp only found out about it after the kid was like 5. Every time he eats crackers he's remembering he has a grandson.
Zoro Cast out on the mountainside by the Spartans for having green hair, the young baby was driven by an instinctive need to become the strongest warrior ever. Kept forgetting which side to hold the shield on so gave up and used two swords instead.
Nami Nami was a baby princess abandoned on a battlefield as her parents were slaughtered, and Nojiko was the princess of a rival kingdom. The two countries went to war over whether tattoos can look good and pretty much wiped each other out. Little girls adopted by a chain smoker and raised as sisters.
Usopp Originally a wooden puppet, Usopp was accidentally fed the Hito Hito no Mi: Model Nose and became a real boy. This is why he gets along so well with other Hito Hito no Mi users.
Chopper Immaculate conception, born to be the true Reindeer Saviour. Wise reindeer from the east followed the red nose by mistake and gave gifts to a reindeer with a nasal tumour.
Robin After her father was killed by a mob boss robbing the circus, Robin was taken in by a rich billionaire with a deep voice and no ulterior motives. But then she got too old and he dumped her on an island with books and a tree.
Franky After his parents were killed by a train, Franky imprinted on the mechanical leviathan and became obsessed with machinery.
Brook After he was kicked out of his school band for having an afro and for playing every instrument better than anyone else, Brook became a solider for the purpose of going to school and killing everyone who ever laughed at him. Then he forgot.
Jinbe Raised by a clam.