This last week, Burger King has released a different patty for their smaller burgers. It's the same thing, except the size is reduced by 20%. They have a star cut wavy pattern around the edges so it is harder to notice.
While they still have their old patties, be sure to order your smaller burger (cheeseburger, hamburger, stacker, etc.) with a Whopper Jr. patty. The size of the Whopper Jr. has not been reduced.