G. Carl Francis was the director at Gotham City's Office of Copyrights.
Joker had hatched the perfect plan to make big money: all fish in Gotham were infected with a special substance so that they shared his infamous grin. By trademarking it, he could get percentage on any sale of fish. For the last part of his plan, he approached G. Carl Francis, Copyrights clerk. Barging into his office, the Joker pressured the clerk to fill in the right copyright form. But much to Joker's dismay, Francis told him that, since fish were a natural resource, he couldn't legally own any trademark relating to them. The Joker threatened Francis to change his mind before midnight, or he's be the unhappiest fish in Gotham. Upon leaving, Harley sprayed him with a cologne.
Francis exposed to Joker venom.
Naturally, Francis turned to the police for help. Commissioner Gordon, Detective Bullock and a squad of cops kept him company, but Francis was worried the Joker might still get to him. Even Batman's arrival didn't calm him down. The Joker made his move by shooting a rocket through the window. It didn't explode, instead, it excreted a gas. It did not harm the cops, but it reacted to the cologne Francis was sprayed with. He fell down laughing, and a grin appeared on his face. Fortunately, Batman administered him with an antidote.
Batman: The Animated Series
"The Laughing Fish"