This dog apparently spent the few months preceding her debut being trained in paranormal hunts. It's just fascinating. She is a beautiful dog and fun to watch. Jason and Grant, the TAPS founders, say she's doing great. I just think she gives us something fun to look at when watching the show.
Ghost Hunters was really the first paranormal show that I'm aware of. Many others have followed like Paranormal State, Ghost Adventures, and Paranormal Cops. The first, it seems like the show may actually outlive all of its competitors. Several of these other shows have had good runs, but have ended or are in the processing of shutting down. Only Ghost Hunters is continuing, and with two spin offs even (Ghost Hunters International and Ghost Hunters Academy).
With Maddie along for the fun, this could go on for much longer than anyone could have imagined.