A man has been found guilty of stealing a rare squirrel monkey from his cage at Chessington World of Adventures.
SpongeBob was found playing with children in a park
Marlon Brown, 23, was among a group who stole the endangered Bolivian monkey from the theme park in south-west London in July 2006.
He denied the theft but traces of his blood were found in SpongeBob the monkey's enclosure, a court heard.
Brown was released on bail and ordered to return to court on 29 March for sentencing at Kingston Crown Court.
SpongeBob's theft sparked a nationwide appeal to the public to help find him.
He was spotted two days later playing with children in Brixton, south London.
'Cruel and irresponsible'
Brown denied theft claiming he did not know his friends were intending to steal the monkey, the court heard.
SpongeBob has since taken up residence at Battersea Zoo, where he is now said to be doing well and a weblog has been started in his name.
Outside the court, Chessington zookeeper Sonia Freeman said: "We are very happy that Mr Brown has been found guilty for being so cruel and irresponsible."
She explained that SpongeBob originally arrived at the zoo as part of an endangered species breeding programme.
"We had hopes for his breeding success," she said. "The futile actions of Mr Brown and his friends have had ongoing serious consequences not only for SpongeBob but also for the rest of the group."