Chapter 661

Chapter 661 is called "A Lake That Spews Forth Coat-Jackers".

Cover Page
From the Decks of the World Vol. 42 - "Impel Down - Warden Hannyabal and Chief Guard Domino".

Short Summary
At the lake near the center of Punk Hazard, Luffy, Zoro, Usopp, and Robin have their ship sunk by centaurs. Zoro moves to attack them, but sharks appear, revealing that the lake is actually part of the ocean. The centaurs attack again, but Brook appears and wounds them, giving his crewmates time to defeat the sharks. Freezing, the group targets centaurs for their winter coats. At the same time, Trafalgar Law takes on Smoker and the Marines, destroying their battleship and rendering them unable to fight. He also switches the minds of Franky, Chopper, Nami, and Sanji.

Chapter Notes

 * Hannyabal and Domino are seen for the first time since the timeskip. Hannyabal is the new Impel Down Warden while Domino is now one of the chief guards.
 * The boss of the centaurs is revealed to be the former pirate Brownbeard, who is shown to be an alligator centaur.
 * One of the centaurs mentions that Luffy, and by extension Zoro, are pirates from the "Worst Generation".
 * Trafalgar Law's Devil Fruit is revealed to be the Ope Ope no Mi.
 * Using the Ope Ope no Mi, Law has swapped Sanji, Nami, Franky, and Chopper's hearts and therefore their minds, putting Sanji in Nami's body, Nami in Franky's body, Franky in Chopper's body, and Chopper in Sanji's body.
 * It is revealed that Tashigi knows about and possesses Haki, though she is not as proficient in using it as Smoker. She is cut down by Trafalgar Law because of her low Haki.