Inside No. 9 is back, with a third series of darkly comic vignettes that deliver chuckles and chills in equal measure.

Keeley Hawes, Philip Glenister and Tamzin Outhwaite are among the stars who've signed up to front Steve Pemberton and Reece Shearsmith's latest string of spooky stories.

Ahead of its launch, the show's creators, writers and stars pulled back the curtain on their twisted anthology, revealing a few of its best-kept secrets...

1. There's one thing that links every single episode

One for the eagle-eyed fans: there's a statue of a silver hare hidden in the background of every single Inside No. 9.

"Each episode is so wildly different," says Pemberton. "There was nothing really linking them other than the fact they were inside No. 9... so we just thought it'd be nice to have an object and hide it on every set."

This content is imported from Twitter. You may be able to find the same content in another format, or you may be able to find more information, at their web site. “@indobleh: Inside no 9 Spot the Hare! It's there each week... pic.twitter.com/kVfAU5KsKl” someone finally spotted it!! — Reece Shearsmith (@ReeceShearsmith) March 1, 2014

There's no special meaning behind the hare though – Shearsmith picked it out at random from a box of props.

Now you know, keep an eye out – though you'll have to pay attention, because the prop isn't always easy to spot: "Sometimes, someone pulls out a photograph of themselves and it's behind them [in the shot]," Shearsmith said. "It's a nice little game we play."

2. League of Gentlemen and Psychoville veterans are banned from the show

BBC/Sophie Mutevelian

Shearsmith and Pemberton have a rule not to hire anyone for Inside No. 9 they've worked with before, though Jason Watkins appears in the first episode of the new series – brilliant comic thriller 'The Bill' – having previously appeared on the duo's Psychoville.

"He broke our rule, because we never have anyone back that we've worked with," says Shearsmith. "But we did with him, because he's brilliant."

The rule is in place "to keep surprising and avoid familiarity" – though we're hoping they might break it again one day to get Mark Gatiss in there...

3. The 'No. 9' is often the last thing they think of

The show's central conceit – that every episode is set inside a "No.9", whether it be a flat, a dressing room or a restaurant – is actually the least important thing about it, according to Shearsmith and Pemberton.

"Sometimes it's the last thing we think about," Shearsmith says. "We think of the idea [for the story] first, not 'What can it be this time?'

"It could really be anything. You could do a body with a tag on the toe with a 9 on it!"

4. They go in blind

The pair never know how an episode will end when they start writing it – they just "find ways within the story to surprise ourselves as we're going along".

BBC/Gary Moyes

"We never quite work out what's gonna happen till the very end," Steve admits. "We just start writing. But it's hard changing it up every single week. A lot of the ideas we've used have been in the bottom drawer for a while... and that bottom drawer's getting a bit empty now!"

5. There's already a fourth series in the works

BBC Two has ordered a fourth series of Inside No. 9 before the third has even aired – and while the series starting next week is "quite a dark" run of episodes, Reece and Steve say they've "gone much lighter" for the following series.

"It's hopefully the silliest," Pemberton says. "We need some laughs!"

6. The next series will include an episode told backwards

Inside No. 9 will be going all Memento in a future episode, which will unravel events in reverse chronology.

Shearsmith and Pemberton say they "definitely like to experiment" with structure in storytelling – having previously filmed 'Cold Comfort' in the style of a CCTV feed, and painstakingly recreated TV horror of the 1970s for 'The Devil of Christmas'.

BBC/Sophie Mutevelian

"It's got to be right for the episode," says Pemberton. "It would be wrong to impose something. But yeah, we've done one in the next series that's in reverse chronology, so that was quite interesting and quite challenging!

"With an anthology, we can do literally anything, so we enjoy setting ourselves those challenges!"

7. There could be a musical episode one day

There might even be an all-singing, all-dancing Inside No. 9, with series three's 'Empty Orchestra' – set entirely within a karaoke booth – originally intended as such.

"It is a kind of musical, because there's music all the way through it," Steve explains. "We do karaoke and we sing the entire song, because we never leave that room!

"I would love to do a proper La La Land-style musical, but I think for now 'Empty Orchestra' ticks that box to some degree."

A full-blown science fiction episode, possibly set in space, isn't entirely out of the question either. "Though we might be wading into Charlie Brooker's world," notes Reece.

8. There's no end in sight for the series

BBC/Sophie Mutevelian

"It's something that could keep going and going and going," Pemberton suggests. "But it is only the two of us writing it, and if we start repeating ourselves, that's the time to get out.

"Hopefully, the audiences are still surprised by what we do... and that's quite a challenge."

9. They won't rule out an Inside no. 9 spin-off

With so many ideas and vivid characters coming out of each episode, could any of the Inside No. 9 outings we've seen so far end up inspiring a full series?

"By the end of the fourth series, we'll have written 24 pilots – that's essentially what they are," Shearsmith says. "Some of them, I have thought, watching them back, that they could be their own thing..."

"But then..." Pemberton chips in. "...people will say we've run out of ideas!"

Inside No. 9 returns to BBC Two for a new series on Tuesday, February 21 at 10pm.

Want up-to-the-minute entertainment and tech news? Just hit 'Like' on our Digital Spy Facebook page and 'Follow' on our @digitalspy Twitter account and you're all set.

This content is created and maintained by a third party, and imported onto this page to help users provide their email addresses. You may be able to find more information about this and similar content at piano.io