Toriko and Komatsu are seen fishing when Komatsu catches a Harusame. After defeating it, Luffy suddenly comes out of the Harusame's mouth and surprises Toriko and Komatsu. Soon, Sunny arrives and Chopper is revealed to be sick. In order to make him feel better, they have to find the "Seafood Fruit" and make Chopper eat it. Thus, Luffy, Toriko and the rest head off to To-Chuka Island.
After Luffy activates Gear Third to defeat some Kung-Fu Mynah Birds, he changes into his chibi form. However, after the timeskip, Luffy no longer has this issue when using Gear Third. It was most likely an error on the part of the animators.