CREATE TABLE table_26961951_4 (us_viewers__million_ VARCHAR2, written_by VARCHAR2)

How many viewers in millions did the Alison McDonald episode get?
SELECT us_viewers__million_ FROM table_26961951_4 WHERE written_by = "Alison McDonald"
SELECT "us_viewers__million_" FROM "table_26961951_4" WHERE "Alison McDonald" = "written_by"