This ruthlessness can have remarkable consequences. Take Mid Life Crisis Man. It starred Charlie Higson, the show's other producer and writer, dressed in pony-tail and leather trousers playing a man in his 40s who has left his wife for a 20-year-old girl.
He rehearsed for months, preparing to move in beside Loadsamoney and the Suits You in the Higson/Whitehouse comedy hall of fame.
Then two weeks before the show was to be broadcast he was dropped. So much for the image of the Fast Show as the product of casual messing about amongst a bunch of funny friends.
Not that you would think so if you spent a day with them. For starters most of the set is given over to fake pubs and the four - Whitehouse, Higson with Mark Williams and Simon Day - spend much of the time off camera taking the piss out of each other. Whitehouse in particular sings, adopts characters and improvises constantly like a hyper-active child.
It gets worse when Bob Mortimer shows up and the studio turns briefly into a fantasy comedy boozer.
Mortimer's contribution to the new series is a character called Thorney Milkwood, who no one on the set seems able to describe: "Well he's just bizarre," says Higson before dissolving into giggles. "His wife sends him out to get things and he brings back stuff he thinks is more interesting... like Squid Ink."
The Fast Show team have the reputation for being approachable and friendly but their lack of celebrity airs can be almost intimidating.
Simon Day, the Fast Show's Competitive Dad and pub irritant, is so surreal you don't know if you're being maliciously or pleasantly mocked. Mark Williams, the potato-faced Brummie of "I'll get me coat" fame prowls around the studio in a black leather box jacket and a pair of white jeans. He looks far more dodgy than Cockney Chris, the show's "I'm a bit whaaay" character.
Higson stands out in this atmosphere. He is quieter, more reserved, perhaps even more middle class. He admits to being shy and Whitehouse describes him as Mr Comedy Governor because he has produced Reeves and Mortimer and looks after the more organisational side of the Fast Show.
Higson also writes strange dark thrillers and once fronted the band The Higsons. This eclecticism may explain why he has a lower profile than Whitehouse who for years has at least been known as "that bloke who is always on with Harry Enfield".
He apparently doesn't like to see his characters described on paper, but some of the new series' selection jump out at you with silly comic resonance: Anxious Poor People Travelling needs little description. Similarly, Roger Nouveaux Football Fan, the man with the picnic hamper at Highbury plugs into the zeitgeist.
Arabella Weir, the main female contributor to the show has replaced Does My Bum Look Big in This? with Woman Who Men Can't Hear and so helps stop the show being too laddish.
But thankfully most of it remains beyond simple explanation. Ted and Ralph, the loverlorn squire and gamekeeper are yet to consummate their love and Jessie is still there, if without his diets: "I don't know what makes `Jesse's Diets' funny," admits Higson. "It just is." Instead of coming out of a shed to tell us what he has mostly been eating, in this series Jesse is giving fashion tips.
The new series' hit catchphrase is likely to come from a new character, dubbed the Filthy Duke. This rakish, Errol Flynn character, the Thirteenth Duke of Wybourne, finds himself in girl's boarding schools and women's prisons at three o'clock in the morning and utters his catchphrase: "What were they thinking of? With my reputation?" which will be applied to a million pub anecdotes by Christmas.
Whitehouse and Higson shy away from any attempt to analyse or intellectualise their comedy, although they have compared the comedy of repetition they use to sex. Its power and humour comes as much from delicious anticipation as it does from the "climax" of the punchline.
The only comedy radicalism they admit to is editing the show so that a running joke can carry across a whole series where most sketch shows will only let a joke run through one episode.
Higson even compares their characters to Seventies innuendo master Dick Emery: "It's not that new an idea. In reality we only do three types of characters: sad characters, mad characters and twats. That's comedy."
`The Fast Show' starts Friday November 14 (BBC2, 9.30pm)Reuse content