Yes, this is a Wizard Of Oz spoof. Lydia is Dorothy, BJ is the Scarecrow, Jacques is the Bone Woodsman, the Monster is the Lion, and Ginger is Toto. But you'll never guess who's the Wizard!
Beetlejuice, Lydia et leurs amis rejouent le Magicien d'Oz. Lydia est devenue Doroty, Beetlejuice l'épouvantail.