As a child, my friend Chris' family in Redlands, CA, had a favorite Chinese restaurant called "No Duh." Really. The family joke, naturally, became, "Are we going out to dinner?" "No duh!"
One night they went out, only to find the restaurant had been sold, and was now called "House of Dr. (somebody or other)," but the somebody-or-other on the sign wasn't working yet. The joke now became, natch, "No duh! House of durr!"
Little by little that became the answer to everything. "Is it dark out?" "No duh! House of durr!"
I loved the phrase so much that I used it for years. "Are you going to the store, Mark?" "No duh! House of durr!"
Five years later I'd left Redlands, was working in La Jolla. Although I hadn't explained where it came from, my girlfriend there picked it up from me. "Going out with Mark tonight?" "No duh! House of durr!"
Her two highschool-age sisters learned it from her. "Surf's up?" "No duh! House of durr!" They passed it on to their highschool beachrat friends. Nobody knew anything about restaurants in Redlands.
One lunch break I took a long walk from the Cove down to Marine Street. Local highschoolers there I'd never met, saying, "No duh! House of durr!"
I'll resist comparing this phrase to a communicable disease, and merely remark on the likelihood of it's having infected the entire Southern California beachfront by this time, along with "tubular," "gnarly," "puffage," and any number of other expressions which undoubtedly have origins which are now equally obscure, yet equally rational.