Up the Establishment! (1968)

Sinopsis: Gustl has married the beautiful Helene. They have a harmonious marriage, the love games are daring, and the Kamasutra is always lying next to the bed. But Gustl still has one wish: to celebrate a real orgy. He suspects that his younger colleagues are always having wild parties. He wants to be one of them, but is never invited to such parties. So he persuades his wife to organize an orgy herself. After much toing and froing, Helene agrees. The two of them put an ad in the newspaper. Like-minded people come forward, Gustl and Helene sort out "suitable" people and get the party underway. When the horde of libido-ready middle-class people arrives at the mattress-lined apartment, there is no sign of Gustl...