The cult comedy troupe - John Cleese, Michael Palin, Eric Idle, Terry Gilliam and Terry Jones - are kicking off their reunion gigs tomorrow and Idle said it will be "really filthy".
Speaking at a central London press conference, Jones joked: "My four-and-a-half year-old daughter is coming to the last show and I dread to think what she will think of it".
Hawking will appear in the show, at London's O2, with Professor Brian Cox and a cast including a full orchestra and dozens of dancers.
Idle said: "He's a big Python fan so he was asked if he would and he said within one minute 'yes'".
Cleese said the show, which includes numerous set changes and special effects, costs around £4.5million to stage.
He said: "It's much more complicated and spectacular than certainly I realised when we sat down for the read through for the first time".
Monty Python's Flying Circus was made for TV between 1969 and 1974 and generations of fans can recite lines and whole sketches.
Sixth Python Graham Chapman died of cancer in 1989 aged 48, and nine years later the five remaining members shared a stage at the Aspen Comedy Festival in the US.
It was announced another 600 tickets would go on sale.