Luffy fights a total of three battles against Caesar Clown.
1. Fight outside the laboratory
Trafalgar Law proposed an alliance to Luffy on Punk Hazard, which the Straw Hat captain agreed to. Part of Law’s plan was to capture Caesar Clown. Luffy was responsible for this task, as he could use Haki to touch the Logia user. Along with Franky and Robin, Luffy joined in the fight with Caesar’s men and the navy that raged at the main entrance of the lab. After a brief skirmish, Caesar Clown emerged, and Luffy immediately threw himself at him.
Luffy was able to tackle the Logia user Caesar using Haki. Unlike sea stones, Luffy was unable to completely disable Caesar’s abilities. With a haki enhanced gum-gum bell, Luffy tried to hit Caesar, but wasn’t fast enough because he turned into gas beforehand. With a huge cloud of poison gas Caesar tried to poison Luffy. The latter inhaled the complete gas, which could not harm him thanks to Magellan’s poison treatment in the Impel Down. Caesar was furious that he was put on the same level as a Paramecia user, but in the next moment took a Gomu Gomu no Jet-Mace and was run into the ground.
Caesar’s subordinates wanted to come to their master’s aid, but he forbade them to interfere. Before Luffy’s next attack could hit, he was hit by Caesar’s Gastanet. Afterwards, he was wrapped up by several pieces of Smiley. Since Smiley was highly explosive, Caesar’s Gastanet caused an even bigger explosion than before. Caesar laughed victoriously until Luffy came up behind him unscathed and threw him far back with a Gomu Gomu no Jet Stomp. The rubber man grabbed the Logia user by the collar, certain he had defeated and captured him. But suddenly Luffy gasped and collapsed. Caesar rose and declared that Luffy had underestimated him.
2. Fight in the lab
Shinokuni, meanwhile, had driven the pirates and the marines inside Caesar’s lab. While the fighting raged in the various blocks, Luffy sought out Block C, where Caesar was holed up with Mone. No sooner had he opened the door to the room than Luffy knocked the scientist out with a punch to the stomach. Before Luffy could grab Caesar like he did in the first fight, Caesar turned into gas and attacked the straw hat with mio gas.
He was able to escape the blast with Gear 2, at which point Caesar asked him why he was even his target. Luffy wasn’t sure of the reason himself, however something interesting would happen should he make it. Caesar then approached him about his alliance with Law, trying to convince Luffy that Law was definitely just using him for his own purposes. Luffy shouted that he would have to decide that for himself and set off on his next attack. Caesar, however, robbed him of the oxygen to breathe with Karakuni. Luffy’s punch missed before he moved to safety, keeping his distance from the scientist.
Luffy had now figured out the distance to stop being caught by Karakuni, as the attack had a certain radius. Caesar laughingly asked him if he could keep fighting like that. Luffy then attacked him with a Gomu Gomu no Jet Pistol, which hit Caesar’s gaseous form in the face. Caesar approached Luffy saying that it hurt and deprived him of oxygen again. He then created a flaming sword and explained that he had other ways to attack Luffy besides poison gas. He tried to hit the rubber man with his Blue Sword, but Luffy dodged it. The scientist set part of his lab on fire.
Luffy gasped for air again, sticking his head up in the air. The next moment he appeared behind Caesar, who turned around with a horrified face. He activated Haki and tried to attack Caesar with a Gomu Gomu no Jet Gatling. However, Mone interfered in the fight and protected her master with a hard snow hut. Luffy managed to break through the snow hut, with Mone stating that the other pirates would not have been able to do so. She stood protectively in front of Caesar and asked him to flee, as this would be a pointless fight. Saying it was inevitable that Luffy would become one of his guinea pigs, Caesar disappeared.
3rd fight: Final
Caesar was with his men in Block R and there he met Brownbeard, who tried to expose Caesar’s true intentions. Caesar, however, struck him down with a muscle relaxant. Just before he could finish off the pirate with Gastanet, a giant fist suddenly appeared next to Caesar. The scientist reacted in such a way that the fist only grazed him. Luffy stood protectively in front of Brownbeard and Caesar ordered his men to return to the 2nd floor. The straw-hatted pirate realized it was all fake while Caesar tirelessly swung one of his speeches. Luffy, however, only gave him a punch right in the face in response, which hurled him into a wall and left a clear imprint.
Caesar then tried to intimidate Luffy, saying that he would eventually have Donquixote Doflamingo behind him. He then attacked him with Gastille; an attack that could even melt steel. However, Luffy dodged this attack before coming up behind Caesar and giving him another blow. As Caesar grew more desperate, he ordered the room’s air vents opened to let Shinokuni in. His men hesitated at first, had they been in such danger themselves. However, they eventually obeyed Caesar, believing that this was for the purpose of deceiving the enemy. They did not expect that Caesar could ever turn a hand against them. As Shinokuni poured into the room, Caesar combined with the deadly poison gas and grew into a giant gas monster.
The next moment, Caesar demonstrated his power by gaslighting his own people. Luffy then ran a short distance into the corridor. Caesar thought Luffy had escaped and declared that there was no longer a safe place on the island. Luffy activated Gear 3 and Busoushoku and ran towards Caesar. He jumped into the room and found himself face to face with the mad scientist. At that moment, Caesar realized he had no chance against Luffy and tried to dissuade him from his attack by offering him a position in his organization. Luffy ignored this offer and hurled Caesar out of the research facility with a gum-gum grizzly magnum.