The Sharks are the local gang in Onett. Their leader is Frank Fly, whom Ness must defeat in order to get to Giant Step, the first "Your Sanctuary" location. The Sharks appear at the beginning of the game, after Ness, Buzz Buzz, Picky, and Pokey Minch defeat Starman Jr. and return Pokey and Picky Minch back to their house. The Sharks consist of three different enemies: The Pogo Punk, Skate Punk, and the Yes Man Junior.
When Pokey knocks on your door when the meteorite lands, he says "...the police that were guarding the meteorite left suddenly to deal with The Sharks. You know the Sharks, they're the local ruffians, and they were really going wild."