The Chucksters' main role in the game is to toss Mario on to certain areas that he cannot reach himself.
Chucksters can be found in areas on Isle Delfino. A single Chuckster can be found on a roof close by to the cannon that leads to Pinna Park. If Mario pays the Chuckster a single coin, he will chuck Mario over to a window that leads to a Shine Sprite.
Numerous of Chucksters can be found during the fifth episode of Pianta Village: "The Secret of the Village Underside." Mario must talk to some specific ones in order to get them to throw Mario to a certain spot. Mario must face an angle to be thrown in the direction a player wants to go.