In One Piece Green: Secret Pieces an early concept of the crew was revealed. Usopp was supposed to be a vice captain/sniper, and have a shorter nose that resembled his father more.
Anime and Manga Differences
In the anime, when the Pacifista was locking onto to Usopp for its next attack, its bounty detector labeled him as Sogeking, even though he was not wearing his Sogeking mask (though his nose or the Kabuto could have given him away).
Although it is a fact that the newspapers (2 years later) managed to recognize Usopp, as he was labeled "Sogeking", proving the Pacifistas have the capability to recognize him.
Usopp's personal jolly roger (post-timeskip) as detailed in the One Piece Magazine.
In addition to the Straw Hats' jolly roger, Usopp also has one of his own, like all the other members of the crew. The flag was first seen when Luffy asked him to design and paint a Jolly Roger for the crew. Though it was supposed to reflect everyone, Usopp designed his own jolly roger as their symbol, reflecting his delusions of captainship. It has Usopp's nose, bandanna, a star, and a slingshot for a cross-bone. Usopp's design was immediately rejected.
Usopp has a second personal jolly roger after the timeskip. In this version his skull is seen on its left side with Usopp's new hat, headphones, and his curly hair tied back. The Kuro Kabuto is seen on its side in the background.
Usopp can be seen in the corner of Luffy's first wanted poster and Zoro's first wanted poster. In Luffy's, he is simply viewed from behind. In Zoro's, his silhouette is faintly seen through the smoke in the background of the poster doing his Crocodile impersonation. However, in the anime, the latter was cut out of Zoro's poster most likely due to the fact that it is not easily visible and was thus overlooked. It was later corrected in Episode 152 but omitted again in the second bounty poster. It is unknown if he is seen on Luffy and Zoro's actual wanted posters.
Usopp's name is possibly based on "Isoppu", which is the Japanese pronunciation of Aesop, the ancient Greek fabulist. Considering that uso means "lie" in Japanese, the name Usopp can be taken as a portmanteau name between uso and Isopp, since Usopp is both a liar and a storyteller. The name is also a Japanese pun in that saying "Ore wa Usopp!" can mean either "I am Usopp!" or "I am a lie!" because Usopp's name is written using Katakana characters and not Kanji.
Were it to be rendered in Kanji, Usopp's name would be written as 嘘風 (Usoppu), meaning "liar way/style".
Usopp's backstory is similar to Aesop's tale The Boy Who Cried Wolf, as he kept calling out that pirates were attacking and so was not believed when pirates actually did come, like the boy when a wolf actually came.
It is possible that Usopp's long nose was inspired by the fairy tale "Pinocchio", as Pinocchio was a wooden puppet whose nose grew longer whenever he told a lie.
Usopp might be somewhat based on the Japanese mythical species tengu, who were said to have long noses and habits of tricking people. Kin'emon even referred to him as a tengu.
In regards to his alter-ego, Sogeking is a play on words as the Japanese word for sniper is "Sogeki".
Ironically, most of the tall tales and lies he told have come true at some point during the Straw Hats' voyage.
There is even a case where one of his bluffs is actually based on truth, though he most likely isn't aware of it. Before reaching Laugh Tale, Buggy came down with the "You'll-Die-If-You-Go-To-That-Island" disease, which is the same bluff Usopp comes up with nearly every time the Straw Hats land on a new island.
He, Luffy, and Sanji claim to have never fallen ill, and thus do not know what it feels like.
Kappei Yamaguchi, Usopp's Japanese voice actor, came up with the notes to the Sogeking song. Oda provided the words and then asked him to develop the notes himself. Kappei also stated that the Sogeking song is the most requested song for him.
Sonny Strait, the FUNimation voice actor for Usopp, has stated several times during the FUNimation DVD commentaries that Kappei Yamaguchi is his favorite Japanese voice actor, saying that whenever he listens to Kappei's performance in recording it is like he is saying "Top that, American voice actor!".
In the 6th Japanese Fan Poll, Usopp was voted the 15th most popular character in One Piece.
Skypiea has a theme park dedicated to Usopp called "Rubber Band Land". It has a drawn profile of him on the overhead sign and a statue featuring him as a muscular warrior, complete with a spear.
The face Usopp made that scared Sugar into unconsciousness is based on the entrance to the Goa Gajah cave in Indonesia.
Usopp's occupation in Wano as a toad-oil merchant seems to be a reference to snake oil, a traditional Chinese remedy without any actual use that became symbolistic for fraud in the West. Ironically, since Wano is based on ancient Japan, the roles would be reversed.
Usopp's birthday, April 1, is known as 'April Fool's Day' (エイプリルフールの日,Eipuriru Fūru no Hi?), a reference to his ability to fool people.