The Delta Brainwave is an essential brainwave that determines the IQ of all living things, robots & plants possess, except Philip J. Fry. He was born without this brainwave because he was his own grandfather due to his "past nastification" with his grandmother during the episode "Roswell that Ends Well." Due to this, his IQ can be very high or very low, as seen in "The Duh-Vinci Code". The Nibblonians sent Lord Nibbler to knock Fry into a cryogenic tube on December 31, 1999, in order to preserve him so that he could defeat the Brainspawn, a species able to control others through this delta brainwave.