This phrase thrived during the late eighties to early nineties in elementary schools through high schools. It is a way of saying "I already knew that, and am surprised this information is new to you."
Kid 1: "Hey, they're coming out with a Super Mario Brothers movie!"
Kid 2: "No durphy, Eddie Murphy."
Kid 2: "No durphy, Eddie Murphy."
by Formula One Jazz Nutjob June 24, 2011