After the smash success of 'The Holy Grail'? Python pitched a religious spoof and.... no one was buying it. So George took it upon himself, with largely his own money, and produced the film: Life Of Brian. While I have issues with that movie, it does have amazing moments and set the course for Python's future en-devours.
Who knew a Beatle could help a Python like that? Sort of... Lion and Mouse eh?