Diego Marquetti-Hill is Didi Martinez-Hernandez's male counterpart in "The Attack of the Counterparts". He is in love with Florence Verlean, and his best friend is David Honea. He was brought to this universe from a parallel universe by Doofenshmirtz. He is a "preppy", and dislikes is wavy hair, so he straightens it. Didi reacts to this by saying, "Are you a tomgirl or something?"