CREATE TABLE table_29685 ("No. in series" FLOAT, "No. in season" FLOAT, "Title" TEXT, "Directed by" TEXT, "Written by" TEXT, "U.S. viewers  ( millions ) " TEXT, "Original U.S. air date" TEXT, "Prod. code" TEXT)

when was the premiere of the episode whose production code is 415?
SELECT "Original U.S. air date" FROM table_29685 WHERE "Prod. code" = '415'
SELECT "Original U.S. air date" FROM "table_29685" WHERE "Prod. code" = '415'