CREATE TABLE table_25664518_3 (first_couple VARCHAR, fourth_couple VARCHAR)

Who was the first couple in the episode having a fourth couple of Sammy and Nat?
SELECT first_couple FROM table_25664518_3 WHERE fourth_couple = "Sammy and Nat"
SELECT "first_couple" FROM "table_25664518_3" WHERE "Sammy and Nat" = "fourth_couple"