Hilarious Morning News Prank as Conspiracy Guest Hurls Coffee into Camera

A Gen-Z'er went all Linda Blair on a Chicago morning show Thursday ... except instead of green slime, a mouthful of java propelled into his camera lens, horrifying a TV anchor.

It went down on WGN in Chicago, where a dude named Peter McIndoe was yakking about his conspiracy theory that birds don't really exist ... rather, the fair-feathered friends are actually drone replicas -- all part of an effort by the U.S. government to keep eyes on us.

As Peter dutifully answers the anchor's questions, he takes a swig of something from his coffee mug and then just hurls into the cam. The anchor is flummoxed ... and it's hysterical.

We're calling BS on this ... but that doesn't make it unfunny.

BTW ... Peter's grassy knoll theory has landed with his fellow Gen-Z'ers ... hundreds of thousands of them are wearing "Birds Aren't Real" t-shirts. They infiltrate various rallies.