Hal Ashby and Peter Sellers, a marriage made in Purgatory.
Ashby was bi-polar, although more manic than depressive. Sellers suffered from social anxiety all his life, he was only comfortable performing. Shampoo and Being There are two of the best political satires ever. Neither fared very well after Being There wrapped.
Arlo Guthrie had a very tough act to follow, Woody is considered an icon of American folk music, influencing Bob Dylan and Neil Young. Correct me if I'm wrong, I've only seen parts of Alice's Restaurant, does the film begin with Woody's passing?