This is the first arc to demonstrate fusing Zoan-type Devil Fruits with weapons; i.e., Lassoo with the Inu Inu no Mi, Model: Dachshund (this would not be seen again until the Enies Lobby Arc). It also foreshadows Dr. Vegapunk's abilities with Devil Fruits. Robin's character is one of the most important issues of this arc concerning the larger story. She introduces the Poneglyphs and the True History, and is the second person to speak about the Will of D. Also, her sad past is foreshadowed.In this arc, Luffy meets his older brother Ace for the first time in three years in Nanohana, who then tells him about his former subordinate, Blackbeard.Also, at that time Ace gives Luffy a Vivre Card, which will be explained by Lola at the end of the Thriller Bark Arc.The paper given in this arc leads to the plots of the Impel Down and Marineford Arcs. Luffy suffers his first and second defeats in a row at the hands of Crocodile,thus beginning a pattern in future fights where Luffy, for the sake of his crew and other people, overtaxes himself physically in long and arduous battles against powerful opponents (Enel, Admiral Aokiji, Rob Lucci, Gecko Moria, Pacifista, Magellan and the Marines). Realizing her own weakness in contrast with the rest of the crew, and wanting to fight for Vivi's sake, Nami asks Usopp to create a weapon for her, which he does in the form of the Clima Tact. Although mistakenly designed as a party trick rather than a serious weapon, Nami still learns to use it to great effect, marking the point of the series where she starts to participate more proactively in battle. During Luffy's third and final battle with Crocodile, the latter explains that once Luffy understands the sea, he will forsake his dream of becoming the Pirate King.These words foreshadow the Post-War Arc: Luffy, after having his spirit broken by Akainu, considers himself too weak to become Pirate King after the death of his brother and being unable to protect his crew, and simply proves that the Straw Hat Pirates, being rookies, are not ready for the threats that inhabit the New World, which will eventually lead the Straw Hat Pirates to individually train in separate locations for two years to prepare for the second half of the Grand Line. Luffy's victory over Crocodile would cause the World Government to label him and his whole crew as a dangerous threat. This is the first arc to fully demonstrate the corruption of the World Government. After Smoker reports to the government of what happened, they ignore his report and give him and Tashigi all the credit and a promotion.