Skidoo (1968)

I can understand why a viewer in 1968 might be offended by going to see a new movie from the director of Anatomy of a Murder and Advise & Consent and getting a movie as incoherent and painfully trendy as Otto Preminger's Skidoo, but seeing it today, we're free to enjoy it on other levels beyond mainstream entertainment: as a time capsule, as an attempt by a successful director to broaden his artistic horizons by adopting what must have seemed like the exciting new styles of such directors as Richard Lester, and as an insane movie artifact where some new piece of lunacy is lurking around every scene. Where else can you find a movie where Jackie Gleason is a retired mobster going out for one last hit on the orders of mob boss Groucho Marx, to eliminate incarcerated gangster Mickey Rooney? Where Austin Pendleton plays a technical genius and LSD enthusiast who doses an entire prison population, leading to a jaw-dropping dream ballet of dancing garbage cans set to the music of Harry Nilsson? Where Frank Gorshin speaks through his grimaced teeth (hilariously) to evade the lip-reading capabilities of the prison's surveillance cameras, and where Carol Channing, as Gleason's wife, belts out the title song ("Skidoo, Skidoo! Between a one and three there is a two!") dressed in a hippie-Napoleon getup while boarding Groucho's yacht hideaway with an army of flower children...it's that kind of movie.
Of course, it's not really very good - the comedy often falls flat, Groucho Marx is a little embarrassing to watch at the very end of his career, and nothing of any real consequence happens. But it's a must-see regardless.