A giant starfish from space, named Starro the Conqueror.
The story starts out with Aquaman being told about the threat by his good friend, Peter the Puffer Fish! Peter tells Aquaman of how Starro appeared, making deputies out of other starfish to help him conquer Earth.
Once Aquaman is told about the threat, he sends out a signal to his friends to let them know that they are needed to save the Earth! First person to receive the signal is Wonder Woman, who quickly leaves the date she is on to help. Hal Jordan is flying an aircraft designed to fly around the world in 24 hours, but he quickly suits up into Green Lantern and wills the aircraft into autopilot. Flash is trying to stop a tornado (which he quickly takes care of), and Martian Manhunter is about to go on vacation. Batman is busy on the tails of some Gotham looters and Superman is busy protecting Earth from an impending meteor threat, so those two decide that the others can manage without them until they finish up their current Business.
Meanwhile, Wonder Woman and Martian Manhunter are at the Hall of Science, where another deputy is attacking. While Wonder Woman is distracting the Starro deputy, Manhunter takes to the upper atmosphere looking for some sort of weapon to take the creature out. J’onn finds some meteor pieces (which he mentions is from the same meteors Superman is taking out at this time) and also uses his super breath. All this causes the Starro deputy to fly off, taking the Hall of Science with it!
Flash follows the deputy to the lake, using vibrations to part waves in an attempt to find it. He then allows the waves to collapse down on the deputy, knocking it out. The mind controlled town folks are released from the deputy’s spell and are able to tell Flash where Starro is located.
Flash takes his new buddy Snapper with him, thinking he might be key to figuring out how to defeat the alien monster. Upon meeting up with the other five Justice League members, Green Lantern decides to take on Starro. A problem arises when Starro reads Green Lantern’s mind and finds out his weakness…the color yellow! The alien turns himself yellow, gaining immunity to GL’s ring.
I do kinda like, though, that the world is basically saved because Aquaman passes on a message from PETER THE PUFFER FISH!!