There is a reference to Planet Zebes (the planet that Samus visited during the original Metroid and Super Metroid) that can be found on the Pirate Homeworld. Land your ship at the Research Facility and find the place on the map called Metroid Processing. Once in this room you will find an empty tank next to the Spider Ball rail. Scan the tank to get the following message: "Data decoded. Zebes specimen. Highly aggressive subject has been transferred to an off-site laboratory."