But particularly so when it’s a cult classic like Good Omens, written by Neil Gaiman and the late Terry Pratchett (he died in 2015, aged 66, after suffering from a rare form of Alzheimer’s disease).
Since the book was published in 1990, it has become “hugely important to people”, notes David Tennant, one of the lead stars of the new Amazon Original series of the same name, which is based on the story.
“When you bump into people for whom this book has meant everything, of course you feel a weight of expectation,” continues the 48-year-old. “And it feels like, since this has been announced, I keep doing that.”
Add in the fact there’s been talk of a Good Omens TV show for years now, and “much-anticipated” really is the term to describe the six-part fantasy-drama, which also stars the likes of Benedict Cumberbatch, Miranda Richardson and Jon Hamm.
However, the pair playing the two main characters are trying not to worry about the pressure of the roles.
“Neil is so involved in it, he’s done the adaptation – I think that helps, obviously,” suggests Welsh actor Michael Sheen, 50, known for TV show Masters Of Sex, and films such as The Queen.
“But it’s hard isn’t it, especially something that hasn’t been adapted before – everyone has their own version in their head of what characters should look like.”
“It won’t mirror what everyone sees in their head but maybe it will be better for some people,” reasons former Doctor Who star Tennant.
“I’m sure some people will be furious, I’m sure other people will be utterly delighted and all you can do is do your best.”
The basis of Good Omens is this: the end of the world is coming. But loose-living demon Crowley, (Tennant) and fussy angel Aziraphale (Sheen), decide to take it upon themselves to stop Armageddon from happening.
First though, they have to find the Antichrist – an 11-year-old boy unaware he’s meant to bring upon the end of days.
As for the relationship between Crowley and Aziraphale, “they’re yin and yang I suppose”, explains Tennant, who’s also famous for TV shows such as Broadchurch and Casanova.
“They’re the very opposite of each other, and yet, because they’ve both been on earth for all these thousands of years, they’ve slightly shifted positions, they’ve met in the middle somewhere.
“He’s an angel who’s not without his flashes of naughtiness and I’m a demon who has been known to do the right thing occasionally.
“Ultimately they would describe themselves as best friends but they could never really admit that. But they do rely on each other – they become attached through the ages.”
We get an insight into this as the series goes on – which allowed for lots of fun dress-up opportunities for the actors.
“There’s a great sequence where we jump cut a few hundred years in time and we see them at Noah’s Ark, we see them in Shakespeare’s Globe, we see them in the Second World War,” reveals Tennant.
They drift towards each other, as they have the “common goal to avert the apocalypse”.
“Really for no other reason than they’re quite enjoying their life,” says Tennant, who is married to fellow actress Georgia Moffett (they have four children together).
What was the appeal of their characters?
“I’ve always been interested in the idea of how we portray goodness,” Sheen divulges.
“The stereotype is that it’s fun to play the baddie because evil’s interesting and goodness is boring, and I think we’re doing a real disservice to ourselves by allowing that to carry on.”
For Tennant, the fact Crowley enjoys life so much, and has got bags of confidence, means “he’s someone rather appealing to get under the skin of”.
“He’s a delicious character because he’s got that supernatural element as well. You can take that in as many directions as your imagination will allow which is fantastically liberating and a really good fun place to start.”
And the actor surmises there’s something we can learn from Crowley’s attitude towards people and life.
“I suppose he’s got a candidness which I think is always something you should probably try and pursue, without tipping over into cynicism – which he probably does.”
The first thing you’ll probably notice when watching Good Omens is how different both the actors look on screen.
Tennant’s hair has been dyed red. “There’s obviously a bit of ginger in my gene pool because it kind of suits my colouring more than I was expecting,” he admits, chuckling – and he has mesmerising bright blue contacts in.
Sheen, meanwhile, has gone a startlingly bright blonde.
“Oh it’s a lot of upkeep!” exclaims the father-of-one (he has a 20-year-old daughter with former partner, actress Kate Beckinsale).
“Fortunately I don’t have to do it – I just turn up and someone does it. But yeah, I don’t know how people do it in real life, that’s a lot of work!
“And now I find myself going, ‘Ooh, look at my roots’. I don’t like my roots coming through!”
Another element of Good Omens we can’t ignore? How timely the story feels.
When we met the cast on set in Oxfordshire, it was all the way back in November 2017, at a time when it felt like the threat of nuclear attack from North Korea was increasing.
“I just pray we make it to transmission!” quips Tennant, while he chats to us during a break from filming.
“It does all feel so apocalyptic on an almost daily basis, that it’s quite a tonic to come to work and to be able to make a joke of the end of the world. Maybe we all need to do that, maybe that makes it all the more relevant.
“I hope that by the time 2019 comes around... It would be nice if it didn’t feel quite so relevant.”
We’ll leave you to decide whether you think that’s the case or not...
Good Omens is available on Amazon Prime Video from tomorrow