Play video content Breaking News SIRIUSXM

Howard Stern says THIS is the single greatest prank call his crew has ever pulled off -- a Peyton Manning impersonator hit up a sports talk show ... and what happened next was epic.

The hosts believed they had the real QB on the line started off by asking about the Super Bowl -- to which "Peyton" replied ... "Cam Newton is a little cry baby bitch."

It gets crazier and crazier from there ... and Howard played the whole thing Tuesday morning on his show on SiriusXM.