Living with ghost-obsessed parents since birth, Teemo had to put up with his parents' "unique" personalities, which often traumatized him. Teemo wanted to be an astronaut when he grew up, and had no interest in hunting ghosts. However, this did not stop his curiosity that one day changed his life forever. While exploring his parents' laboratory, Teemo accidentally activated the newly-built Fenton Ghost Portal, causing his molecular structure to become infused with ectoplasm. Teemo became half-human and half-ghost and gained ghostly superpowers.

Teemo wears a pink hat which matches his shirt, and has blue pants and shoes. His hair is colored brown. He has blue colored eyes and buck teeth. He, along with his friends Heimerdinger and Ziggs, are considered unpopular at school.