Gerard Mystery is Martin's father and Diana's step-father. He married Diana's mother when Martin and Diana were very young. Unlike his immature son, Gerard is a very rational, logic-minded like Diana and considers anything related to the paranormal to be "balderdash". As a scientist, he spends much of his time in the forest doing field work. In the third season, he finds out about "The Center" and that Diana and Martin work for it as well. Voiced by Michael Donovan.