A 12-year-old boy impaled his right arm on a fence in Brooklyn while playing tag with his friends on Monday, officials said.

The youngster, whose name was not immediately released, was playing at about 6:45 p.m. on St. Marks Avenue in Crown Heights when he jumped onto a trash-can lid.

When the lid came off, the boy slipped and fell onto a wrought-iron fence about 3-feet high, according to police and his pals.

Medics rushed him to Kings County Hospital with the piece of the fence still stuck in his arm. A cop called him “a real trooper.”