Diana Lombard is a serious, rational, obsessive, straight, 16-year-old student with nothing in common with her step-brother. As an agent at "The Center," she strives to bring more seriousness into Martin's life She is Martin's female counterpart during investigations. Diana is at times quite jumpy and squeamish on missions, but shows great courage when called on. Not sharing Martin's love of the paranormal, she often tries to explain something with logic before it becomes apparently paranormal.
Diana has the hardest time keeping her cool with her irresponsible step-brother, and will generally slap, kick, beat or scream at him quite often. Regardless of Martin's quirky behavior, she loves him like her own real brother. She seems to be the bait on the majority of the missions and the "damsel in distress". Diana usually loses bets to Martin. She is probably the second or first victim in the episodes including being cocooned by an acid spewing insect queen, becoming an evil half human-half spider, and being possessed by a vengeful spirit at a mountain lodge. When Martin is transformed by the monster, Diana uses her own skills to save him. In few episodes Diana wears Martin's U-Watch and uses it when he loses it while being transformed. Voiced by Kelly Sheridan.
- Has two signature hair clips.