Finn the Human

Finn Campbell Mertens (also known as Finn and Finn the Human) is a fictional character and the main protagonist of the American animated television series "Adventure Time" created by Pendleton Ward. He is voiced by Jeremy Shada in most appearances. 
The character first appeared in the original pilot, where he was named Pen and voiced by Zack Shada, Jeremy's older brother.
The character has been met with largely positive critical reception.
Finn's enthusiastic nature becomes more serious as the series progresses, meaning he is both maturing and developing as a character as he ages. As shown in "Memories of Boom Boom Mountain", Finn appears to have been abandoned in the woods when he was a baby.