While in space, Batman and Superman become possessed by brain creatures. The brain creatures ultimately take over the minds of Wonder Woman, Robin, and Aquaman when it appears that the Wonder Twins are successfully defeating Batman and Superman's asteroid attack of Earth. Batman and Superman, while under mind control, continue to attack Earth by firing huge asteroids at the surface. Superman uses his speed to hurl multiple asteroids at Earth's surface, which causes fissures, fires and floods. Wonder Woman uses her mental powers to overcome the mind control and with the help of a magnetic cloud the brain creatures are expelled from the brains of Wonder Woman, Aquaman, Robin, Batman, and Superman. Wonder Woman then devises a plan to send an electric current throughout Earth and trap the brain creatures, after which Superman uses a laser gun and sends the brain creatures many light years away from Earth.

A crooked space circus proprietor, Zarnum, uses a device to turn protected animals that have been illegally captured into beasts to boost attendance at his space circus. Sensing that the Super Friends are on to his scheme, he uses the device to change Wonder Woman, Aquaman, and the Wonder Twins into space creatures. It is up to the rest of the Super Friends to track down the elusive space circus, rescue the captive Super Friends, and bring an end to the poaching that has been taking place. 
NOTE: Zarnum's name is loosely based on circus legend P.T. Barnum.