CREATE TABLE table_23575917_6 (first_broadcast VARCHAR2, davids_team VARCHAR2)

When david o'doherty and katherine parkinson are both on the davids team when is the first broadcast?
SELECT first_broadcast FROM table_23575917_6 WHERE davids_team = "David O'Doherty and Katherine Parkinson"
SELECT "first_broadcast" FROM "table_23575917_6" WHERE "David O'Doherty and Katherine Parkinson" = "davids_team"