CREATE TABLE table_78475 ("Week" FLOAT, "Date" CLOB, "Opponent" CLOB, "Result" CLOB, "Game site" CLOB, "Attendance" CLOB)

Which Opponent was played on 1991-10-13?
SELECT "Opponent" FROM table_78475 WHERE "Date" = '1991-10-13'
SELECT "Opponent" FROM "table_78475" WHERE "Date" = '1991-10-13'