Debra Messing, 44, who stars on Smash as Broadway lyricist Julia Houston, has listed her showstopper in Bel-Air for $11.995 million.

The traditional-style house, designed by architect Paul R. Williams and built in 1937, features bay windows, updated interiors, a den, a bar, a gym, four fireplaces, six bedrooms and eight bathrooms in 6,400 square feet. The more than half-acre gated property, sheltered by tall hedges, includes a pool, a cabana and a brick driveway.

Homes by Williams, who was popular among celebrities and designed homes for entertainers such as Frank Sinatra, Lucille Ball and Desi Arnaz, still attract big names. Messing bought the property from actress Renee Zellweger in 2003 for $7 million, public records show.

Tennis CHAMP

Tennis superstar Serena Williams’ Westwood condo is in escrow. The listing price is $1.85 million.

The Wilshire Corridor building, constructed in 2001, offers concierge service, a valet, a pool and spa and a gym. The open-plan unit features city views, two bedrooms, 3.5 bathrooms, a den/office, a fireplace, balconies and a direct-access elevator.

Williams, 31, has been ranked the No. 1 female player in the world five times by the Women’s Tennis Association. FLUX CAPACITOR NOT INCLUDED

Actor Christopher Lloyd, 74, known to moviegoers as quirky scientist Dr. Emmett Brown in the Back to the Future sci-fi trilogy, has sold his house in Montecito for $5.1 million.

Lloyd built the Umbria-inspired home after the house he had on the five-acre site was destroyed in a 2008 wildfire. The single-level house, which has ocean and mountain views, features a double-island kitchen, four bedrooms, 4.5 bathrooms and 4,600 square feet of living space. There is a pool, a spa, gardens, fountains, an expansive lawn and a bocce ball court.

A BIT OF MAYBERRY

The former home of Don Knotts in Glendale, for sale at $1.295 million, is in escrow.

The Colonial Revival house, built in 1934, has been restored and updated. Features include a foyer that steps down to the living room, wood-beam ceilings, a decorative fireplace, coffered ceilings in the dining room, a breakfast room, a den, three bedrooms, two full bathrooms, a three-quarter bath, a powder room and 3,213 square feet of living space.

Knotts, who died in 2006 at 81, was known for his role as bumbling Deputy Sheriff Barney Fife in The Andy Griffith Show during the ‘60s, about the same time he owned the house.

The sellers paid $600,000 for the property in 2003, public records show.

‘REAL’ HOUSEWIFE

Faye Resnick of The Real Housewives of Beverly Hills has purchased a home in the Hollywood Hills for $1.605 million.

The traditional-style house is surrounded by mature landscaping and sits on slightly more than half an acre with fruit trees, patios and a pool. Features include an open floor plan, hardwood floors, a living room fireplace and a wall of French doors in the dining room that open to a balcony with treetop views.

There are three bedrooms, 3.5 bathrooms and 2,567 square feet of living space.

EXORCISM OF SORTS

Exorcist film editor Bud S. Smith and his wife, sound editor Lucy Coldsnow-Smith, have sold their Hollywood Hills home of more than 40 years for $880,000.

The Smiths’ hillside storybook cottage-style home, built in 1926, is surrounded by patios and gardens. Features include a step-down living room with high ceilings and a fireplace, two bedrooms and a separate one-bedroom guest apartment.