A recurring boss in the Kirby series, Whispy Woods is usually the first boss enemy Kirby has to face in his adventures. He is known for being one of the easiest bosses for Kirby to fight - He's a (usually) stationary tree that drops apples on Kirby to attack, so all Kirby has to do is inhale the apples that drop and spit them back at him while standing next to him to avoid the air bullets he spits out. Whispy has appeared in many games ever since the very first one and sometimes takes a spot other than Level 1 in a game, and sometimes even changes strategy and gains new attacks, but that doesn't make him any tougher. A similar boss named King Golem who appears in Kirby & The Amazing Mirror also shares the same attack pattern as Whispy.
In the anime, Whispy takes a different role. Instead of being a major enemy, Whispy serves as an ally to Kirby and his friends. He is very kind to his friends, yet shows no mercy to those who threaten his kingdom and forest. At first, he thought Kirby and his friends were intruders and tried to crush them as punishment. But after realizing King Dedede used him, Whispy becomes Kirby's friend while Dedede tries many times to cut down his forest (yet fails every time). In the Super Smash Bros. games, Whispy appears in the background, often minding his own business before taking deep breaths and then blowing strong winds that push players close to the edges of the Kirby stages he is placed in.
For more info, see his wiki page.