I remember seeing a clip of this as a kid when it happened. I was both slightly terrified and hugely intrigued. From Vice Motherboard:
Right up until 9:14 PM on November 22nd, 1987, what appeared on Chicago’s television sets was somewhat normal: entertainment, news, game shows. That night, as usual, Dan Roan, a popular local sportscaster on Channel 9’s Nine O’Clock News, was narrating highlights of the Bears’ victory over the Detroit Lions. And then, suddenly and without warning, the signal flickered up and out into darkness.
In the control room of WGN-TV, the technicians on duty stared blankly at their screens. It was from their studio, located at Bradley Place in the north of the city, that the network broadcasted its microwave transmission to an antenna at the top of the 100-story John Hancock tower, seven miles away, and then out to tens of thousands of viewers. Time seemed to slow to a trickle as they watched that signal get hijacked.
A squat, suited figure sputtered into being, and bounced around maniacally. Wearing a ghoulish rubbery mask with sunglasses and a frozen grin, the mysterious intruder looked like a cross between Richard Nixon and the Joker. Static hissed through the signal; behind him, a slab of corrugated metal spun hypnotically. This was not part of the regularly scheduled broadcast.
Finally someone switched the uplink frequencies, and the studio zapped back to the screen. There was Roan, at his desk in the studio, smiling at the camera, dumbfounded.
“Well, if you’re wondering what’s happened,” he said, chuckling nervously, “so am I.”