"The Laughing Fish" is the forty-sixth episode of Batman: The Animated Series. It first aired on January 10, 1993. Joker unleashes a toxin into Gotham City's harbors, causing all the fish affected to mutate into "Joker fish", with a deformed smile clearly resembling his own. Batman analyzes the fish and finds that the chemical is non-toxic to humans, so Joker is not trying to poison people. Instead, his plan is far more bizarre: He attempts to copyright the fish, and thus gain a percentage over all sold in the Gotham area.