They think it sounds contemptibly stupid, beneath even the lowest conception of television dignity, unwatchable and even unmakeable.
"I laughed ridiculously about it when they suggested it," says Lenora Crichlow, the 25-year-old actress who plays the ghost, Annie.
"To be honest, my reaction was, `Are you serious?' I take my acting quite seriously.
"I'd just quit a heavy drama. This sounded like an absurd joke."
And it was, kind of.
Toby Whithouse, the show's creator, had filled entire cemeteries with discarded Being Human scripts.
The one Crichlow saw had been written in the giddy certainty that it would never be produced.
"By the last one, I just assumed the show would never be made," Whithouse admits.
"And the moment I realised that, it completely liberated me.
"Nothing I've ever written was ever easier."
But Being Human turned out to be anything but the campy, supernatural rip-off of Three's Company that everybody expected.
Instead, it's a wistful, witty and sometimes scary meditation on whether life is wasted on the living.
Even more surprisingly, it's a (pardon the expression) monstrous hit in Britain and the United States.
Even now, nobody who works on Being Human can quite believe its success.
"It had never really occurred to me that the show might air in the US," Whithouse says.
"One doesn't want to tempt fate.
"It had already been a long and exhausting process getting it to the screen.
"I was just grateful anyone was watching it and enjoying it.
"A life beyond that, I didn't want to think about it."
TV shows that go bump in the night are hardly a novelty on television; from The Vampire Diaries to Supernatural, TV has more fangs and phantasms than you can shake a crucifix at.
What distinguishes Being Human from the werewolf pack is the way the characters' struggles with their supernatural sides complicate the ordinary romantic and workplace dramas of 20-somethings.
Annie the ghost has to stand by, jealously and invisibly, watching her old boyfriend take up with another girl.
George the werewolf (played by Russell Tovey) must explain to landlords why the furniture is reduced to a heap of kindling every time there's a full moon.
And Mitchell the vampire (Aidan Turner) no longer dates because his kisses inevitably result in something much more gruesome than hickeys.
Their relations with God are even more problematic.
When George tells Annie he's no longer an Orthodox Jew and can eat bacon, she inquires, "Do they have rules about being a werewolf as well?".
George, his mordant wit wrapped around a core of despair, replies: "I think you'd be hard-pressed to find a religion that doesn't frown on it."
If the show's characters emphasise their humanity, it's because they were originally written as humans.
Being Human started out as a sort of fractured suburban version of Friends.
"I was hired to devise a show about three college-graduate friends who decide to buy a house together," says Whithouse, a British TV veteran who had written a comedy-drama series about nurses as well as the occasional episode for such sci-fi series as Torchwood and Doctor Who.
"I thought it wasn't a particularly thrilling idea, and then - completely unbidden - I had the thought of making the three characters a recovering sex addict, a borderline agoraphobic and a very repressed guy with anger-management issues.
We liked the way the characters locked together, but we couldn't come up with a story.
We decided to have last meeting, and if we couldn't come up with it, we'd call it a day."
That final meeting dragged on until somebody said, "What if we make George, the guy with the anger-management issues, into a werewolf? At least that would give us a story for the first episode".
From there the addict quickly turned into a vampire and the agoraphobic into a ghost who couldn't leave the apartment because she was murdered in it.
"But everybody was still sceptical, and none more so than myself," Whithouse says.
"I wrote the first version as a sitcom ...
"
Then I decided to do a complete rewrite from page one.
"This time, I pretended I was writing a low-budget American indie film ... but always, in every version, the bottom line was the characters, the original ones we came up with."
The gritty indie-film approach worked, at least as far as Whithouse was concerned.
After airing the pilot in February 2008, BBC decided it wasn't worth a full-series run and ditched the project.
It relented only after several months of viewer uproar.
By then most of the actors had signed on to other projects and had to be recast.
"The show was always a hit, just not with the channel," says Crichlow, who wasn't in the pilot.
• Being Human screens Wednesdays at 9.30pm on Prime.
