In every chapter, the post-timeskip Straw Hat Pirates meet up with new and old characters and have adventures with them.
Unlike the main series, there is no overarching plotline, and every chapter is a self-contained gag story. Characters and elements from throughout the manga and movies may appear or be referenced, but many of the stories are original.
One Piece Party has two original characters, who appear in one chapter each, as detailed below. None of them are considered canonical.
The young son of Drip, who genuinely believes that his father is the pirate Sanji. He unexpectedly visits the Thousand Sunny to visit his father during work, and the Straw Hat Pirates pretend that Drip is the cook to avoid disillusioning him.