Return From Witch Mountain or Wicked Stepmother. It's more a missed opportunity than a complete disaster, with a plot that has potential for social commentary but is executed clumsily, and a tone that can't seem to decide between surrealism and slapstick. In a very different pairing from their turn as working-class parents in 1956's The Catered Affair, Davis and Ernest Borgnine team up as two misfits who dress up like hippies and rob a bunch of banks in New Mexico. Davis' Bunny is a lonely old lady who loses everything when the bank forecloses on her house (which for some reason involves immediately demolishing it). Borgnine's Bill is a junk collector who snatches up Bunny's plumbing to sell for scrap, but he's also an escaped convict who'd been in prison for robbing banks.
Inexplicably, Bill offers Bunny a ride after her house is torn down, then immediately tries to get rid of her. When that doesn't work, he reluctantly agrees to teach her how to rob banks, and after coming across a group of hippie protesters outside one branch, they decide to don costumes for their heists. Jack Cassidy plays an oblivious, pompous detective who's hot on their trail and so obsessed with the depravity of contemporary youth that he refuses to even consider that the bank robbers might not be young people. There's a lot of near-satire here, and some of the plot devices are just so bizarre that you can't help but laugh. Bunny and Bill wear the exact same outfits to every robbery and never get recognized, and Bunny is motivated primarily by her pathological need to provide for her two ungrateful adult children (one of whom is played by an amusing John Astin). The detective hires a young college student to be his consultant on youth matters, and then proceeds to fondle and seduce her at every opportunity, even while she's clearly two steps ahead of him in solving the incredibly obvious crimes.
Unfortunately director Gerd Oswald doesn't seem to know how to play up the satirical elements, and most of them just fall flat. Davis ended up suing the producers for butchering the story and cutting her dialogue in post-production (she clearly says "fuck 'em" as the movie's last line, but it's dubbed in as "screw 'em"), and she was obviously hoping for something with more bite to it. But Bunny O'Hare is still worth seeing for Davis fans or fans of counterculture exploitation; it's never been released on VHS or DVD, but it plays on TV sometimes and is available at the moment on Netflix Instant. If nothing else, the moment when Cassidy's detective places a single canary feather in his filing cabinet under "F" (for "feather") nearly redeems the whole thing.