Batman: The Animated Series

Season 1

Episode 46: The Laughing Fish

Fishermen discover that Gotham's fish all have the Joker's colors and signature smile. Batman investigates, and realises that the Joker is hoping to make money off of these new fish by having them trademarked. After two government employees are nearly killed by Joker toxin, Batman examines that specific fish, and sees that it is actually a Japanese one, meaning that the Joker is hiding at the Aquarium. Bullock tracks the Joker down, but is captured and used as live shark bait as part of a trap for Batman.