All the dialogue of the four debaters on the TV show (excluding the obvious dream sequences) is lifted verbatim from the actual show.
Rufus Jones plays both Terry Jones and Michael Palin's wife. This is in fitting with the Monty Python sketches, in which Terry Jones usually played most of the female characters.
Michael Palin and Terry Jones liked the film, but John Cleese hated it and also disliked Darren Boyd's portrayal of him.
In the style of Monty Python, several cast members have multiple roles.
Eric Idle rattles off a list of people who might send him a box full of excrement, and names The Beatles. This is actually unlikely, as George Harrison was a producer of Life of Brian.