It all started one morning....

The reasoning revealed!!

Usopp ate a gender-changing devil fruit. 

 Sanji (never seeing a devil fruit thought it was a tropical fruit) placed it in the fruit bowl. 

 Usopp decided to eat a snack before he went to bed.

Usopp was weeping on the floor, which Zoro thought was stupid.

Zoro the feminist icon.

"Curse you Sanji! "
"I should snipe his face!"
"Why do tits hurt?"
"Sanji that bastard!"

Everyone decided that Usopp was the same.

Chopper whispered something in Usopp's ear, and whisked him or (her?)away.

Sanji was having a hard time.

Usopp the woman? Or Usopp the ugly guy?

But oh no. Usopp was hot. Beautiful curly hair, full lips that looked luscious on Usopp, and oh. Those eyes!

Nami was having a good laugh about this one. Usopp, being hot as a woman? oh, what a laugh. Nami could dress her... oh the outfits will be fun.

Franky was having a crisis. Is Usopp little bro or little sis? Bro? Sis? GOD DAMN IT

Brook was plotting a sentence that we all know he is going to say (in which a fire star will be thrown into his face)

Zoro just thought Usopp was hot. Anyway, time for a nap.

Jinbe was simply confused. How should he refer to his crewmate? Ugh, devil fruits. The fishman was having a very hard time deciding.

Robin was simply plotting something. But what?

Chopper and Usopp came back an hour later, with a happy Chopper and a nervous Usopp.

"Hey, guys! "Usopp's condition is permanent, but we don't know how much he changed. "He does have the woman's genitalia.

"But's up to Usopp on what he wants to be called or slash treated."

Chopper explained, quickly but clearly so they will understand.

Usopp then pointed at them.

"Listen here! "I was a man, but now I am a woman, I will be referred to as a woman! "I might as well do the part that I was given. "I shall be called... Goddess Usopp."

"No." All of them responded to Usopp.

Usopp sulked.