Batman Beyond: The Call
One day, Starro sunned itself on a rock as a strange craft appeared in the sky. It never occurred to Starro to be scared, until it was too late to flee. Being the last of its kind, Starro became an object of the Preserver's interest and was included in his collection of unique specimens. Starro tried repeatedly to escape, but to no avail; it simply was not strong enough to escape the Preserver's enclosure. Years later, the alien was rescued by Superman and placed in his Fortress of Solitude. Though it was still little more than a prisoner, now Starro had a plan: Starro decided to gain control of Superman since it witnessed the Kryptonian's strength.
Starro makes its move on Superman. Decades later, Superman was feeding Starro when it jumped up at his face and grabbed hold of him. From that moment on, Starro took psychic control of Superman. During the subsequent years, the alien remained concealed under his costume and used Superman to breed thousands of psychic-parasitic clones. It planned to release the creatures into the ocean and thus conquer the world.
Starro/Superman chases Batman. When the time came to enact its plan, Starro/Superman attempted to dispose of the Justice League Unlimited (presumably in fear they might jeopardize its plans). After nearly killing Micron, Starro/Superman enlisted Batman's help to find the traitor among the JLU ranks (most likely to sidetrack everybody). But when Starro/Superman failed to do away with Warhawk, Superman was exposed as the culprit though the team wasn't aware of Starro's existence. Starro/Superman retreated to the Fortress of Solitude, where he was confronted by the JLU. After Superman was subdued by a shard of Kryptonite, the heroes discovered Starro attached to Superman's chest. Realizing it was a water creature, Aquagirl made telepathic contact with it, uncovering its plans. The tables were soon turned, however, when Starro's spawn took over Aquagirl, Warhawk, Kai-Ro and Big Barda. Starro/Superman was released, and went in pursuit of Batman. After crashing the Batmobile, it let its guard down and Batman tackled it with an electrocuting grapple. Starro was stunned and lost its mental grip on Superman, who managed to break free. Starro was subdued while Batman and Superman fought off its brethren. When finally all the alien starfish were contained, Aquagirl made contact with Starro and was able to determine the location of its home planet. She input the coordinates into Big Barda's Mother Box, and then Starro and its spawn were safely boom-tubed back home.
Batman The Brave and Bold
Starro is an alien conqueror that resembles a gigantic version of an Earth starfish. It goes from planet to planet and exerts its mind control powers as well as using psychic clones to take over the minds of individuals. However, Starro's campaign came to a halt when it arrived in Happy Harbor, Rhode Island on Earth. It was defeated by the Justice League. Starro attempted many more times to take over Earth but failed, including during a battle against Batman and the Green Lantern Guy Gardner. The fight was captured on camera and described in a newspaper article.
Starro's first appearance in Batman the Brave and the Bold was in the episode Revenge of the Reach! where the Challengers of the Unknown were investigating a meteor that crashed on Dinosaur Island. When the meteor opened, Starro clones were unleashed, and quickly took control of the Challengers. The apparent herald of the invasion, The Faceless Hunter, then unleashed Starro clones upon Atlantis. They quickly took over everyone, including Fluke and eventually Aquaman himself. Even Adam Strange and his people of Rann fell prey to the clones. Over time, hundreds of heroes were brought under Starro's control. Those not susceptible to mind control such as Red Tornado were destroyed and the preparation for the coming of Starro the Conquerer began.
The Starro invasion finally came to the breaking point and with most of the world's heroes under his control, the Faceless Hunter started to summon his master. Despite the best efforts of a rag-tag team of heroes led by Batman, including Firestorm, Captain Marvel, Booster Gold and B'Wana Beast, Starro reached Earth. The heroes tried to fight him and after an extended battle Captain Marvel (in his Billy Batson form) destroyed Starro by summoning his magic lightning. The lightning was unable to reach Billy due to Starro hovering over them and struck the beast instead. Upon realizing this, Firestorm urged Billy to summon the lightning again and again, which killed Starro. (The same trick did not work as well in the second half of the story, when The Faceless Hunter found a way to combine all of the "dead" Starro spores into a giant semi-humanoid "Starro" beast.)
In other media
Starro appeared in special episode of Robot Chicken about DC heroes, where he fights against Justice League and Legion of Doom.
Batman The Brave and Bold