Lord Nibbler (voiced by Frank Welker) masquerades as an innocent, cute and unintelligent pet during most of the series. In reality, he is a highly intelligent Nibblonian and capable of communication, but tries to avoid suspicion while he protects the Earth in general and Fry in particular from the Brainspawn. As with all Nibblonians, Nibbler's feces consist of dark matter, which can be used as starship fuel. It is an extremely dense material, "each pound of which weighs over ten thousand pounds," according to Professor Farnsworth in the season 1 episode, " Love's Labours Lost in Space." After he accidentally reveals to the Planet Express crew that he can speak in Bender's Big Score, he forgets to wipe their memory of his intelligence, which it turns out does not affect them much, and from then on he speaks freely to the crew. In the pilot episode, Nibbler's shadow can be seen as Fry falls into the cryogenic freezer, alluding to the reveal in the fourth season episode " The Why of Fry " that he helped send Fry to the future.