It’s a bird, it’s a plane . . . it’s Brian Cashman?

Yes, in fact, it was the Yankees general manager who scaled down the outside of the 22-story Landmark Building in Stamford, Conn., yesterday morning.

“I was thinking of the Batman and Robin stuff,” Cashman told the Associated Press afterward. “It’s pretty incredible. It’s the opportunity of a lifetime.”

Cashman was strapped into a safety harness to assist him down the building, and was cheered by firefighters and organizers holding the cable when he reached the ground. Cashman was practicing for a holiday show set for tomorrow, in which he will help Santa Claus make the same trip.

He made two separate runs down the building — the second time wearing reindeer antlers over a wig of spiked hair.

“I wouldn’t let any players do that,” he said. “I’m replaceable.”