From Bulbapedia, the community-driven Pokémon encyclopedia.
Sullivan (Japanese: スズムラ Suzumura) is a character of the day who appeared in Whiscash and Ash.
A self-proclaimed "fishing god," Sullivan's ultimate goal is to capture a Whiscash named Nero. For years, Sullivan tried countless of times to capture the Pokémon, but he always failed. He hoped that with the help of Ash and his friends, he would finally achieve his goal. Ash wanted to capture Nero as well, since the Pokémon had eaten his Badge case.
Although Sullivan was declaring himself a fishing legend, it was Ash who finally caught Nero on a fishing rod, managing to force it onto land and weaken it with Grovyle's Pound attack. After a foiled attempt at capturing Nero by Team Rocket, Sullivan sent out his Flaaffy, Hannah, against Nero and decided to use his secret weapon - a Master Ball. He threw it, but the Water/Ground Pokémon opened its mouth and ate the Ball.
Although stunned that his Master Ball had been eaten, Sullivan vowed to never give up on trying to capture Nero, claiming that the hunt would always be exciting for him. Wishing Ash luck on his next Gym battle, he said that they were welcome to stop by whenever they felt like fishing.
Sullivan is easily manipulated by the words of others. He became immediately depressed whenever Max inadvertently insulted him or his fishing methods/advice and managed to do a perfect cast on the first try. This seems to have been directed at Max specifically, however, because when Ash caught Nero on his first day of fishing, Sullivan did not have the same depressed reaction as before. When he was upset by Max, however, he became perky and cheerful again whenever Ash, May, and Brock referred to him as a fishing legend.
- Sullivan's outfit has a symbol of a Whiscash on the back.