It looks like the promotion replaces last month's Free Coffee Fridays on the BK website. Perhaps this portends to Burger King running a different value promotion every month? (Update 12/14: The promotion is running through January 16, 2011)
The Original Chicken Sandwich was Burger King's longer, thinner analog to the McChicken back when the McChicken was McDonald's flagship chicken sandwich before McDonald's value-sized (and value-priced) it. An Original Chicken Sandwich costs $3.99(!) in the Los Angeles area.
