Chucksters are a variant of Piantas in Super Mario Sunshine. They are capable of throwing Mario a good distance behind them or above them. This is especially helpful for speedy nearby navigation. Talking to a Pianta is often what reveals them as a chuckster, as they throw Mario immediately afterward.
This ability appears to be developed and practiced, as is the case with two particular Piantas in Ricco Harbor. As the player unlocks and plays through more episodes, they become more skilled at tossing Mario, to the point where they are both able to do so with good results.
A particular chuckster is found on the roof of one of the buildings in Delfino Plaza. If he is spoken to and given a coin, he hurls Mario behind him, into the building in which the Shine Sprite is held. If thrown off-target, Mario may miss the building and must speak to the chuckster again for another attempt.
The angle at which Mario speaks to a chuckster is a major factor for where he will wind up afterward. This concept is the focus of the bonus area of Pianta Village, which features a variety of chucksters. Some must be spoken to at a specific angle to either move on to the next or collect items.