Theo is quite childish, happy-go-lucky, fun-loving, and occasionally stubborn. He doesn't understand the consequences in serious situations, meaning that Tari often has to look after him. He often just accepts that he's going to die in most bad situations, which annoys and concerns Tari.

He is inspired by SMG4's incarnation of Mario, meaning that he isn't the brightest, but does care for his friends, particularly Tari. This makes him a comedic relief most of the time.