The paranormal thriller stars Desperate Housewives actress Williams and Lost star Terry O'Quinn as the owners of a haunted building.
"It's a very seductive place and [our characters] are a very seductive couple," she told TV Guide. "You want to be them and live where they live."
Williams also revealed that she had felt unsettled when her real-life daughter played an unexpected role on the show.
"There's one scene where my character talks about the tragedy of losing her daughter, Sasha, and they needed a girl who was 22 years old to be in a photo," she explained.
The 49-year-old offered up a photo of her own 22-year-old, also named Sasha, admitting: "Yes, it was a little strange."
Dave Annable (Brothers & Sisters) and Rachael Taylor (Charlie's Angels) will also star in 666 Park Avenue alongside Williams and O'Quinn.
The series will air on Sundays at 10/9c on ABC this fall.
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Watch the trailer for 666 Park Avenue below: