We don't know if this is real or not . . . because it's so ridiculous.  But someone posted a video on YouTube of a guy with a mullet on a talk show in the late '80s or early '90s.  And he shows off his ridiculous talent . . . of whistling with his mouth open.
The talent itself is hilarious, but so is the guy.  In addition to the outstanding mullet his facial expressions are AMAZING.