CREATE TABLE table_3966 ("Operator" TEXT, "Number purchased" FLOAT, "Variant" TEXT, "Bodybuilder" TEXT, "Year ( s )  purchased" TEXT)

Who is the operator when willowbrook was the bodybuilder?
SELECT "Operator" FROM table_3966 WHERE "Bodybuilder" = 'Willowbrook'
SELECT "Operator" FROM "table_3966" WHERE "Bodybuilder" = 'Willowbrook'