Coreen Fennel becomes known to Vicki during her first "unusual" case, hiring her to find out who killed her boyfriend. Once the case was over, she managed to insinuate herself into the position of Vicki's office assistant. Coreen appears to have extensive knowledge about the occult, and is certainly far more curious and accepting of it than any of the other characters. Because of this, she seems to have struck up a friendship with Dr. Sagara, a professor of the occult known to Henry, and the two can occasionally be seen working together on a case for Vicki.

Coreen serves as an emissary at times between Vicki and Mike, usually trying to get Vicki talking with him again. It was shown various times that she may have a crush on Henry, most prominently when first meeting him. However when the two rarely work together, Coreen's lingering looks may suggest that she has a crush on him or it may be the way Henry naturally attracts women. This character does not appear in the books beyond the "client" role she originated in the first episode, and it has been suggested that she "replaced" the character of Tony. Several sources cite the omission of Tony as being due to copyright reasons in that the rights to the series of books that feature Tony are owned by another network. Fan sites claim that there were aspects of Tony's free-spirited, reformed street hustler character that might have proved offensive or unsettling to the general viewing public.