Coco Jumbo is a small land turtle (亀) whose main characteristic is a key-shaped hole on top of its shell, in which a special key allowing people into its Stand can be placed. Prosciutto describes it particularly as being 'dark' in color.
The series is known for alternating colors between media, the information presented below may or may not be canon.
Despite being an animal Stand user, Coco Jumbo doesn't display any kind of personality or heightened intelligence whatsoever. It seems to, like all turtles, prefer to hide in small, dark places.
By the end of Vento Aureo, Coco Jumbo's body became permanently affixed to Polnareff's soul, gaining his personality and allowing him to speak to humans.
When a special key is placed in the hole on its back, people can access a small room within the turtle.
Nothing much is known about Coco Jumbo. It is assumed that Diavolo used the Bow and Arrow on it, giving Coco Jumbo its current abilities.
Coco Jumbo is introduced idling in Naples' train station. At first, Bucciarati doesn't take any interest in it, looking for a keyhole corresponding to the key he retrieved earlier. Soon, he notices the keyhole in the turtle's back and realizes what its power is. During their adventure, Coco Jumbo serves as a room for Team Bucciarati as they travel through Italy, allowing them to sneak aboard various means of transportation and providing a safe room for any injured protagonist.
Coco Jumbo plays a key role in saving the lives of both Bucciarati and Trish Una during their first encounter with Diavolo. Giorno Giovanna takes DNA from the turtle and turns it into one of his ladybug brooches using his Gold Experience and hands it to Bucciarati as a tracking device. When Giorno begins sensing that something has gone wrong the moment Bucciarati's phone is destroyed by Diavolo, he turns the brooch back into a clone of Coco Jumbo, who sucks the Boss into itself, stalling him long enough to allow Bucciarati to come up with a plan in order to escape with Trish.
During Chariot Requiem's switching of souls, Jean Pierre Polnareff's is transferred into Coco Jumbo's body where it assumes direct control until after Chariot Requiem is eliminated. Polnareff would later permantently reside in Coco Jumbo's body, having his soul trapped in Mr. President as a ghost.