Rented Lips

Rented Lips is a 1988 comedysatire film directed by Robert Downey, Sr., and starring his son, Robert Downey, Jr., as well as Martin Mull, Dick Shawn, and Jennifer Tilly.

A documentary film maker, whose most recent work is Aluminum, Our Shiny Friend, is offered the chance to shoot his long dreamt of musical on Indian Farming Techniques if he completes the shooting of a porn film financed by an evangelical church and uses the same crew and cast for both films.Sometime after its theatrical run, International Video Entertainment released the movie on VHS. The movie has not been released on DVD and as of December 21, 2009, Lions Gate has not announced any plans for a DVD release. ........

Source: Wikipedia