CREATE TABLE table_2818164_2 (production_code INT, original_air_date VARCHAR)

What's the production code of the episode originally aired on February 21, 1985?
SELECT MIN(production_code) FROM table_2818164_2 WHERE original_air_date = "February 21, 1985"
SELECT MIN("production_code") FROM "table_2818164_2" WHERE "February 21, 1985" = "original_air_date"