Muriel's Wedding, The Adventures of Priscilla: Queen of the Desert, and Strictly Ballroom. An unofficial trilogy of films from the early '90s that are known as small cult items elsewhere but were absolutely massive hits here in Australia, and are regarded as classics; I think you're actually legally mandated to watch them all in succession if you're applying for citizenship here.

Also, every Australian, more or less without exception, can quote the TV series Kath and Kim on command. ("Kimmy, look at moi." "I'm gropable!" "It's noice, it's different, it's unusual", etc.)