Theo is the the main protagonist and the grandson of Guardian Purple. Theo is tall for his group, with spiky black hair and bright blue eyes.
He's very heroic, but he can also be very stubborn. Theo is a bit selfish at the start of the series, but grows less so as it progresses. Despite being Guardian Purple's grandson, he is completely unaware of the seven food groups until the first episode of the series, and remains in the dark about much of the conflict. He is heavily implied to have feelings for Lena, and responds with anger and jealousy when he believes she has feelings for Sid. He even mocks Lena and Sid when they were off looking for Sid. In episode five he offers to help Lena's cold and is emotionally hurt when Lena is mad at him. In episode one he tries to carry her up a building but she wouldn't let him. In another episode, Theo and Lena are separated while Theo is off getting a submarine, Lena is left behind on Alex's ship. Once reunited, they can't help but hug each other.He has a crush on Lena during the series.