The Brain Spawn were a sentient species that came into existence during the Big Bang. They invaded planet Earth during the 31st century. They looked similar to human brains, and used telekinesis to move around. Their leader is the Big Brain who lives in the Infosphere. The species had an ability to make people stupid; the only one immune to this power was Fry, due to lacking the delta brain wave after traveling in time and becoming his own grandfather.
They were responsible for destroying some planets like Space Rome, Don Martin 3, and Tweenis 12.
After their initial defeat on Earth, the Brain Spawn began constructing a massive Infosphere, where they collected all the information in the universe. They planned to destroy the universe in order to stop the creation of any new information once the task had been completed, but were foiled by Fry and the Nibblonians.