The Extra Long BBQ Cheeseburger is pretty much two Rodeo Cheeseburger merged into one. It was first introduced earlier this year and features two flame-grilled beef patties side-by-side (alas, no extra long beef patty), topped with American cheese, onion rings, and barbecue sauce on a toasted long sesame bun.
Burger King's Two for $5, Mix & Match deal allows you to buy any two sandwiches/burgers from a rotating selection for a discounted price of $5. The current selection includes the Extra Long BBQ Cheeseburger, Big Fish Sandwich, Big King, or Original Chicken Sandwich.