CREATE TABLE table_1952 ("No. in series" FLOAT, "No. in season" FLOAT, "Title" CLOB, "Directed by" CLOB, "Written by" CLOB, "Original air date" CLOB, "Production code" CLOB)

What was the original air for the 06-03-521 production code?
SELECT "Original air date" FROM table_1952 WHERE "Production code" = '06-03-521'
SELECT "Original air date" FROM "table_1952" WHERE "Production code" = '06-03-521'