Look, up in the sky! It’s a bird . . . it’s a plane . . . it’s a beach house?

A duplex penthouse at 24 Horatio St. in the West Village, which was just listed for $8.9 million, has some nifty inclusions — a private elevator entry, painted brick walls and a corner great room with a wood-burning fireplace.

But its star feature can be found on the private roof terrace: a 2001-built one-bedroom, coral-tone “bungalow” suite. A New York Times story from that same year says it’s akin to a “Santa Monica beach house with views west to the Hudson River, south to Wall Street and east to the Empire State Building.”

The 385-square-foot structure, designed by Michael Pierce and DD Allen, of Pierce Allen, really does evoke seaside California, with its walls of windows and a beamed ceiling. It’s invisible to passers-by (it was built far back from the building’s parapet, according to landmark requirements); and currently fits a lime-green sofa, a bathroom and a galley kitchen.

The unit’s owner, Joellin Comerford, has owned the pad since 1996. She shelled out $400,000 to build her beachy rooftop spread.

“I have 14 nieces and nephews,” she told the Times. “I wanted them to be able to sleep over. I wanted them to have their own mini-world.”

Grown-ups were allowed up, too, for holiday gatherings. Comerford, a managing partner at Accenture Ltd., also hosted baby showers and wedding showers there.

Robby Browne, Chris Kann and Jennifer Ireland Kubis of Corcoran Group are repping this listing.