The Pirates Festival is a non-canon event said to occur at various points over the years, where pirates come together and interact. A special Pirates Festival was held in the film One Piece: Stampede as part of Douglas Bullet's plot to become Pirate King.
According to Boa Hancock, Pirates Festivals happen every few years, with no real established interval between them. Before the one in Stampede, no Festivals had been held in 20 years. Due to the massive number of pirates in close proximity to each other, the Festival is said to be a lawless and dangerous event. Actions like fighting, stealing, and even kidnapping are permitted without issue. The only rule of the event is that the attendees must keep it a secret, ensuring that the Marines do not find out about it.
Pirates come to the Festival by invitation, with most of the attendees typically being the Grand Line's most infamous pirates including Super Rookies and the Seven Warlords of the Sea. A small amount of the invitees are not pirates, as shown when the bounty hunter Cidre was invited, likely for the purpose of starting conflict. Civilians may also be invited to sell food and wares, such as Takoyaki 8. Invitees receive an Eternal Pose that allows them to navigate to the island where it is held.
Buena Festa's Festival
Several events were being held during the Festival, for everyone to enjoy.
Miss Pirate Competition
A beauty contest with a cash prize. Nami participated and won it.
Main Event: The Treasure Race
The main event was a treasure race to obtain which was an Eternal Pose pointing to Laugh Tale. However, the event was a trap designed for Bullet to kill all the pirates in attendance as part of his quest to become Pirate King. Bullet and Festa also arranged for the Marines to unleash a Buster Call on Delta Island during the Festival in order for Bullet to kill the Marine Admirals as well.
Three additional crews participated in the Pirates Festival: the Fischer's Pirates (フィッシャーズ海賊団 Fisshāzu kaizoku-dan?), the Announcers Pirates (アナウンサーズ海賊団 Anaunsāzu kaizoku-dan?), and the Ippon Oubo Pirates (イッパン・オウボ海賊団 Ippan oubo kaizoku-dan?). The Fischer's Pirates are the main protagonists of Fischer's X One Piece, a spinoff manga starring the Japanese YouTubers Fischer's. The Announcers Pirates are voiced by guest voice actors, and the Ippon Oubo Pirates are voiced by winners of a general application. However, the latter two crews' members were not identified in the film, and they were only listed in its credits.