Happy Trees are the main entities encountered in Happy G Toon Adventure.
They are crudely-drawn, two-dimensional trees with cartoonish faces. Their sprites are animated in a way commonly used by games of this style; they constantly alternate between two slightly different sprites to make them seem more "drawing-like". Unlike characters in AEwVS and ABiBaZ, they don't always face directly towards the camera.
There are two varieties: oak trees, which are female, and pine trees, which are male.
If not interacted with, they will sometimes look around at each other, or at the player if they are nearby. They randomly laugh or make other happy-sounding noises. If the player "kisses" them, they will blush and laugh some more.
However, if the player approaches them with an axe or other weapon, all trees around the player will scream and stare in shock. If the player hits one of them with a weapon, it will be chopped down and spurt blood onto the ground or walls around it. All other nearby trees will become horrified and will scream in shock, and killing more trees will increase this effect.