Egg Pirate

Egg Pirates are humanoid pirate-themed robots created by Dr. Eggman. They can only be found in Sonic Adventure's Casinopolis stage aboard a large decorative pirate ship, running about the deck in a fixed pattern. The robot's don't have organic batteries like most of Eggman's robots and will release rings if they are destroyed.

It is possible that Dr. Eggman may have anonymously sold the Egg Pirates to Casinopolis as part of their chosen theme for the establishment and may serve no real purpose other than as an animatronic attraction.